History of the study of the placenta. The location of the placenta is normal and pathological. Possible deviations in the development of the organ

18.04.2019

Placenta (synonym baby place) is an organ formed during pregnancy and provides a connection between the mother and the fetus. Through the placenta, in the process, nutrition, respiration of the fetus, and excretion of metabolic products are carried out.

Placenta at the end of pregnancy: 1 - fetal surface; 2 - mother surface.

The placenta has the form of a disc with a diameter of 15-20 cm, a thickness of 2-4 cm and a weight of 500-600 g (1/6 of the weight of the fetus). The surface of the placenta, facing the fetus (fetal part), is covered with amnion (see), smooth, it attaches to it (see), from which branching vessels depart (Fig., 1). Mother part- the surface is dark red, divided into lobules - cotyledons (Fig., 2), covered with a decidual membrane (see).

The fruiting part of the placenta is formed by the chorionic plate (shell). The villi extend from the chorionic plate. Each villi is supplied with capillaries from the umbilical vessels. The villi of the placenta of a full-term fetus are covered with a layer of syncytium.

The maternal part of the placenta (basal plate) is formed by a compact layer of the decaying membrane and a layer of cellular trophoblast. Septa (septa) depart from the basal plate, dividing the placenta into lobules; the septa do not reach the chorionic plate. From 180 to 320 spiral arteries pass through the basal plate from the uterine wall to the placenta. The maternal blood flowing through these vessels is poured between the villi into the so-called intervillous space (the space between the basal and chorionic plates). From the placenta, the mother's blood flows into the marginal sinus and into the veins located in the basal plate. Thus, two blood flows are carried out in the placenta: one is maternal in the system uterus - intervillous space - uterus and the second in the system - umbilical cord - villi - umbilical cord. Fetal blood and mother's blood do not mix and are separated by the syncytium covering the villi and their capillaries. This membrane is conventionally called the placental barrier. The surface of contact of the villi with the mother's blood is very large - 6.5 m 2.

Oxygen to the fetus comes only from the mother's blood flowing into the placenta. In the placenta, some of the substances pass through the cell and tissue membranes from the mother's blood into the fetal blood and back by simple diffusion; in addition, "active transport" is carried out. So, water exchange occurs through the placenta in both directions very quickly (3500 ml / hour). The transition of fats and proteins through the placenta is carried out as a result of complex biochemical processes with the participation of the placenta. Some medicinal substances penetrate through placental barrier this depends on their molecular weight as well as their lipoid solubility.

The placenta produces chorionic gonadotropin(see. Gonadotropic hormones), similar in properties to the pituitary gonadotropin. The secretion of human chorionic gonadotropin in the first weeks of pregnancy is used to hormonal diagnostics pregnancy (see Ashheim - Tsondeka reaction,). The secretion of the hormone reaches its maximum by the third month of pregnancy. During pregnancy, the placenta secretes estrogen hormones (see), progesterone, which is identical to the hormone corpus luteum; the secretion of progesterone gradually increases from the third month to the end of pregnancy. provides a decrease in the excitability of the myometrium.

Pathology... In severe (edematous) form of hemolytic disease of the fetus, the placenta is very large and the ratio of its weight to the weight of the fetus is 1: 3 and even 1: 2; at each birth, not only should be weighed, but also the placenta with the membranes of the fetus. With the edematous form of hemolytic disease of the fetus, the placenta has a pale red color, is edematous, the maternal surface is coarse; with syphilis in individual cases the placenta can also be swollen and large. Often white infarctions are found in the placenta - well-demarcated areas of villous necrosis. Heart attacks are often observed with late; with a significant number of heart attacks, fetal death may occur. Often, in the normal placenta, deposits of grains of lime are visible on the maternal side; they are always available during post-term pregnancy.

V obstetric practice great importance have abnormalities of attachment of the placenta (see).

The placenta (from the Latin placenta - a flat cake; synonym for a child's place) is an organ formed during pregnancy and provides a connection between the organisms of the mother and the fetus. The placenta, developing from the membranes, mainly from the villous (chorion) and decidua (see) of the uterus fused with them, is the main part of the placenta. Through the placenta, nutrition, respiration of the fetus, as well as the excretion of metabolic products, are carried out.

The development and structure of the placenta in different types animals are very diverse. The human placenta belongs to the hemochorial type, since the trophoblast fetal egg destroys the endothelium of the mother's capillaries, and the chorionic villi (see) extract nutrients and oxygen from the mother's blood.

In the first weeks of development of the ovum, the trophoblast especially grows (see. Embryo). The mesenchyme does not grow into the distal ends of the villi, and cell clusters are formed here. The cells bordering the decidual tissue and mixing with its elements are cytotrophoblast cells (K.P. Ulezko-Stroganova). The villi that connect to the decidua are called attaching or anchoring (Fig. 1). By the end of the third month, the villi of the smooth chorion atrophy, and the placenta begins to form from the branched chorion. The growth of the placenta occurs due to the intensive branching of the villi. Distinguish between the fetal and maternal part (side) of the placenta. The fruit part is formed by the chorionic plate and covered with amnion; the umbilical cord with its blood vessels is attached to it. The branches of the vessels of the umbilical cord pass through the chorionic plate and stem villi extend from it. The maternal part of the placenta (basal plate) is formed due to the compact layer of the decaying membrane and the layer of cellular trophoblast. Between the basal and chorionic plates there is an intervillous space (Fig. 2), in which maternal blood circulates.

Rice. 1. Anchor villi and cytotrophoblast cell accumulations.
Rice. 2. Scheme of the structure of the placenta according to Shtiva: 1 - decidua; 2 - placental septum; 3 - chorionic plate; 4 - the trunk of the villi; 5 - amnion; 6 - umbilical vessels; 7 - intervillous space.
Rice. 3. Cross section through the villus in early stage pregnancy: 1 - syncytium; 2- kidney-shaped growths of syncytium; 3 - syncytial giants; 4-layer of Langhans cells; 5 - villus vessels.
Fig. 4. The septum between the cotyledons at the point of its attachment to the basal plate.

As pregnancy progresses, the trophoblast cells of the basal plate are completely degenerated in places, and then the fibrinoid layer delimits the intervillous space; the latter from the side of the chorionic plate is delimited by a layer of Langhans cells (Fig. 3).

After four months, septa form in the placenta, which start from the basal plate towards the chorionic plate, but do not reach it (Fig. 4). These septa divide the placenta into lobes (cotyledonis), clearly visible from maternal side placenta (on average there are 16-20). The septa do not completely separate the intervillous space, and it is uniform under the chorionic plate (Fig. 5).

Rice. 5. Blood circulation in the intervillous space (according to Spanner): 1 - uterine artery; 2 - intervillous space; 3 - marginal sinus; 4 - maternal veins; 5 - placental septum.

The placenta of a full-term fetus is a lozenge-like body, 15-20 cm in diameter, up to 3 cm thick and weighing 500-600 g.

In the intervillous space, blood enters from the uteroplacental vessels, spiral arteries, and flows back to the uterus through the uteroplacental veins. Blood in the intervillous space circulates slowly, since the uteroplacental vessels are relatively small, and the intervillous space is extensive and the pressure in it is about 10 mm Hg. Art.

In the intervillous space, the villi are immersed with the terminal branches of the vessels of the fetus enclosed in them (Fig. 6). Metabolism, including gas exchange, occurs through the wall of the capillaries of the villi and their integumentary epithelium.

Rice. 6. Vascularization of the villi.

There is no communication between the fetal blood circulating in the villous vessels and the intervillous space. The blood of the fetus and the mother circulates in systems independent of each other and does not mix anywhere.

V big circle the circulation of the pregnant woman includes the uteroplacental circulation.

Physiology... The placenta carries out between the body of the mother and the fetus all the variety of metabolic processes occurring through the surface of the chorionic villi. By the end of pregnancy, the surface of the villi reaches 6,000-10,000 cm 2, and their total length is 50 km. Morphological and functional features The placenta, which allows to regulate the penetration of various substances from the mother's blood to the fetus and back, is considered as a placental barrier. The placenta contains mechanisms that facilitate the transition from mother to fetus of various substances necessary for its development. The fetus receives oxygen, nutrients, water, electrolytes, vitamins, antibodies from the mother through the placenta, and transfers carbon dioxide and toxins to the mother. The placenta also produces some hormones, inactivates and destroys others, activates the activity of enzymes. The placenta contains many enzymes that break down carbohydrates, proteins and fats, as well as respiratory enzymes and all known vitamins (especially C); proved the ability of the placenta to synthesize glycogen, acetylcholine (EM Berkovich). All this turns the placenta into a unique formation that simultaneously performs the functions of the lungs, intestines, liver, kidneys and endocrine gland.

The barrier separating the blood of the mother and the fetus in the intervillous space consists of the epithelium of the trophoblast or syncytium covering the villi, the connective tissue of the villi and the endothelium of their capillaries. In the terminal villi, many capillaries are located immediately below the syncytium, and the barrier consists of only two unicellular membranes.

The placenta has complex mechanisms that determine the process of placental transmission. Syncytium and cytotrophoblast, which make up the cover of the villi of the placenta, are highly active in resorption, enzymatic cleavage and synthesis of many complex substances. Perhaps these derivatives of trophoblast are involved in the regulation of the transition of substances from mother to fetus and vice versa (V.I.Bodyazhina). The placenta is able to inhibit or delay the transfer of certain substances from mother to fetus and from fetus to mother. However, the barrier function of the placenta is limited. If the transition of gases, proteins, fats, carbohydrates and other substances that are constantly present in the blood of the mother's body is regulated by fairly precise mechanisms that develop in the placenta during its evolution, then in relation to substances that enter the body accidentally (medicines, toxins, etc. ), the selective function of the placenta is adapted to a lesser extent, and the mechanisms regulating their transition are imperfect or absent.

Barrier function the placenta is carried out only under physiological conditions. It is important to take into account that the gradual thinning of the syncytium as the gestational age increases, leads to an increase in the permeability of the placenta. Holes and gaps are formed in the syncytial cover of the villi (K.P. Ulezko-Stroganova).

The exchange of gases (oxygen, etc.) and true solutions through the placental membrane occurs according to the laws of osmosis and diffusion due to the difference in the partial pressure in the blood of the mother and the fetus; the transition of proteins, fats, carbohydrates and other substances - as a result of complex biochemical processes with the participation of the placenta, which has a variety of enzymatic functions.

There are different concentrations of potassium, sodium, phosphorus and other substances in the blood of the mother and fetus. The mother's blood is richer in proteins, lipoids, neutral fats, glucose, and the fetal blood contains more protein-free nitrogen, free amino acids, potassium, calcium, inorganic phosphorus, etc.

Passing speed medicinal substances through the placental barrier is associated with the degree of their ionization and lipoid solubility of undissociated molecules; non-ionized substances with a high solubility in lipoids penetrate the barrier quickly. The placental barrier protects the fetus from the penetration of harmful substances only partially. Drugs, alcohol, nicotine, potassium cyanide, mercury, arsenic, antibiotics, vitamins, hormones, some antibodies, viruses, toxins, etc. penetrate the placenta. The permeability of the placental barrier to harmful substances and microbes increases with pathological changes in the placenta associated with complications of pregnancy and childbirth, as well as damage to the villi by microbes and their toxins.

The placenta is a temporary endocrine gland that produces gonadotropins and progesterone. The place of formation in the placenta of gonadotropic hormones (see) is Langhans cells and clusters of trophoblast cells.

Estrogens in the placenta are produced by the trophoblast initially in not a large number, and in the future, the production of hormones increases. In the mature placenta, estriol is found predominantly, estrone is found in a smaller amount, and estradiol is found even less. Estrogens affect the anterior lobe of the pituitary gland, the interstitial brain, the autonomic nervous system of the mother, as well as a number of vital important processes and especially on liver function.

Until the 4th month of pregnancy, progesterone is produced by the corpus luteum of the ovary, and later, with the extinction of the function of the corpus luteum, mainly of the placenta. An increase in progesterone with the development of pregnancy is confirmed by an increase in the amount of pregnandiol excreted in the urine. Estrogens and progesterone, especially their quantitative ratios, are of great importance for physiological development pregnancy and fetus (see Pregnancy), the onset and regulation generic activity(see Childbirth).

Placenta(placenta - children's place). The placenta is an extremely important organ that unites the functional systems of the mother and the fetus.

By outward appearance The placenta looks like a round, flat disc. By the beginning of labor, the mass of the placenta is 500-600 g, diameter - 15-18 cm, thickness -2-3 cm.

In the placenta, two surfaces are distinguished: the maternal, adjacent to the wall of the uterus, and the fetal, facing the amnion cavity.

The main structural and functional unit of the placenta is considered cotyledon(placenta) - a lobule of the placenta formed by the stem villi of the 1st order with branches extending from it - the villi of the I and III orders (Fig. 18). There are from 40 to 70 such lobules in the placenta. In each cotyledon, a part of the villi, called anchor, is attached to the decidua; the majority floats freely in maternal blood circulating in the intervillous space.

In the intervillous space, there are 3 sections: arterial (in the central part of the cotyledon), capillary (at the base of the cotyledon), venous (corresponding to the subchorial and interlobar spaces).

From the spiral arteries of the uterus, blood under high pressure flows into the central part of the cotyledon, penetrating through the capillary network into the subchorial and interlobar sections, from where it enters the veins located at the base of the cotyledon and along the periphery of the placenta. Maternal and fetal blood flow do not communicate with each other. They are separated by the placental barrier. The placental rear consists of the following components of the villi: trophoblast, basement membrane of trophoblast, stroma, basement membrane of endothelium of fruit capillaries, endothelium of capillaries. At the subcellular level, 7 layers of different electron densities are distinguished in the placental barrier. In the terminal villi, the exchange between the blood of the mother and the fetus takes place through the placental barrier. The most favorable conditions for exchange are created in the second half of pregnancy, when the capillaries move to the periphery of the villi and closely adjoin the syncytium with the formation of syncytiocapillary membranes, in the area of which transport and gas exchange directly take place.

The functions of the placenta are complex and varied.

Respiratory function consists in the delivery of oxygen from the mother to the fetus and in the removal of carbon dioxide in the opposite direction. Gas exchange is carried out according to the laws of simple diffusion.

Nutrition the fetus and the excretion of metabolic products is carried out through more complex processes.

Placental syncytiotrophoblast produces specific proteins and glycoproteins, has the ability to deaminate and transaminate amino acids, synthesize them from precursors and actively transport them to the fetus. Among the lipids of the placenta, 1/3 are steroids, 2/3 are phospholipids, the largest part is neutral fats. Phospholipids are involved in the synthesis of proteins, the transport of electrolytes, amino acids, and promote the permeability of the cell membranes of the placenta. Providing the fetus with products of carbohydrate metabolism, the placenta performs a glycogen-forming function until the beginning of the active functioning of the fetal liver (IV month). Glycolysis processes are associated with the concentration of glucose in the blood of the mother and fetus. Glucose passes through the placenta by selective diffusion, with more than half of the glucose coming from maternal blood serving to nourish the placenta itself. The placenta stores vitamins and regulates their supply to the fetus, depending on their content in the mother's blood.

Tocopherol and vitamin K do not pass through the placenta. Only their synthetic preparations penetrate to the fetus.

The placenta has transport, storage and excretory functions in relation to many electrolytes, including the most important trace elements (iron, copper, manganese, cobalt, etc.). Placental enzymes are involved in the transport of nutrients to the fetus and the elimination of fetal metabolic products.

By doing hormonal function, the placenta, together with the fetus, forms a single endocrine system (fetoplacental system). In the placenta, the processes of synthesis, secretion and transformation of hormones of a protein and steroid nature are carried out. The production of hormones occurs in the trophoblast syncytium, decidual tissue. Among the hormones of a protein nature in the development of pregnancy, placental lactogen (PL) is of great importance, which is synthesized only in the placenta, enters the mother's blood, and supports the function of the placenta. Chorionic gonadotropin (CG) is synthesized by the placenta, enters the mother's blood, and participates in the mechanisms of fetal sex differentiation. Prolactin, synthesized by the placenta and decidual tissue, plays a certain role in the formation of the lung surfactant.

From the cholesterol in the mother's blood, pregnenolone and progesterone are formed in the placenta. Placental steroid hormones also include estrogens (estradiol, estrone, estriol). Placental estrogens cause hyperplasia and hypertrophy of the endometrium and myometrium.

In addition to these hormones, the placenta is capable of producing testosterone, corticosteroids, thyroxine, triiodothyronine, parathyroid hormone, calcitonin, serotonin, relaxin, oxytocinase, etc.

Possessing systems for the synthesis of humoral factors that inhibit the mother's immune-competent cells, the placenta is a component of the system immuno-biological protection of the fetus. The placenta, as an immune barrier, separates two genetically foreign organisms (mother and fetus), thereby preventing an immune conflict between them. A certain regulatory role is played by the mast cells of the stroma of the chorionic villi. The placental barrier is selectively permeable to immune factors. Cytotoxic antibodies to histocompatibility antigens and IgG antibodies easily pass through it.

The placenta has ability to protect the body of a baby from the adverse effects of harmful factors that have entered the mother's body (toxic substances, some drugs, microorganisms, etc.). However, the barrier function of the placenta is selective, and for some damaging substances it turns out to be insufficient.

During pregnancy, unique anatomical formations and even new organs appear in the female body. One of them is the placenta. Without her, it is impossible to imagine the development of a baby in mother's womb... This article will tell you about what the placenta is, how it is formed and what functions it performs.

Characteristic

The placenta is a special embryonic organ. It is typical not only for humans, but also for other mammals. The appearance of the placenta in the female body cannot be imagined without the chorion.

Its formation begins to occur after a fertilized egg is implanted to a specific wall of the uterus. Subsequently, a specific formation appears around it, which can be called a chorion. Its membranes later begin to transform and transform into placental tissue.

Scientists have found that for the first time chorion appears in the body of a pregnant woman within 7-12 days from the moment of fertilization. It takes some time for the transformation to the placenta. On average, it is several weeks. For the first time, the formed placental tissue appears only by the beginning of the second trimester of pregnancy.

The placenta acquired its name for a reason. This specific organ, formed only during pregnancy, has been known to doctors since antiquity. Agree that it is not difficult to notice it. During childbirth, after the birth of the child, the placenta is also born. This feature contributed to the fact that the placenta long time called the afterbirth. It should be noted that this name has survived to this day.

From Latin, the term "placenta" is translated as "cake". This name almost completely characterizes the appearance of the placenta. It really looks like a cake. Doctors often refer to the placenta as a “baby's place” as well. This term is often used even in the medical literature.

Structure

The placenta of pregnant women has a heterogeneous structure. In fact, it is a unique organ that must perform a huge variety of different functions. Any disturbances in the structure of the placenta can be very dangerous due to the development of pathologies. The presence of structural defects placental tissue causes a violation of the normal course intrauterine development fetus.

For reliable attachment to the walls of the uterus, the placenta has special outgrowths - villi. Through them, there is a reliable fixation of the placental tissue to the wall of the uterus. This feature also determines the interaction between the small embryo, placenta and endometrium.

The umbilical cord is located between the placenta and the fetus - this is a special organ that, in fact, connects the baby with his mother at a biological level. This unique bond will last until birth. Only after the birth of the baby is the umbilical cord cut, which means the birth of a new person.

The umbilical cord contains important blood vessels - arteries and veins. Outside, they are surrounded by a special substance - "Warton's jelly". It has an interesting texture that resembles jelly. the main objective of this substance - reliable protection blood vessels of the umbilical cord from exposure to various negative factors external environment.

In the normal course of pregnancy, the placenta remains in the female body throughout pregnancy. Her birth takes place after the birth of a baby. On average, the placenta is born 10-60 minutes after the baby is born. The difference of this time interval in different kinds depends on many factors.

The entire tissue of the placenta can be conditionally divided into 2 parts - maternal and fetal. The first is directly adjacent to the uterine wall, and the second to the fetus. Each part of the placenta has a number of unique anatomical features.

Mother part

This area of the placenta is formed largely on the basis of the decidua, or rather, its basal part. This feature determines the special density and structure of the maternal part of the placenta. The surface of this area of the placental tissue is rather rough.

The presence of special septa, which are present in the placenta, ensures the separation of maternal and fetal blood flow. The placental barrier prevents maternal and fetal blood from mixing at this stage. A specific "exchange" begins to occur somewhat later. This is due to the actively proceeding process of osmosis and diffusion.

Maternal part of the placenta

Fruit part

This part of the placenta is covered with a special amniotic layer. Such a structure is necessary so that a special water environment is subsequently formed in the uterine cavity, in which the baby will "live" for several months of its intrauterine development.

On the fetal side of the placenta, there is a special chorionic formation, which ends in numerous villi. These villi are involved in the formation of an important element - the intervillous space.

Some of the villi are called anchor villi, as they are tightly fixed to the uterine wall, providing reliable fixation. The rest of the outgrowths are directed to the intervillous space, which is filled with blood from the inside.

Decidual septa (septa) divide the surface of the placental tissue into several separate parts - cotyledons. They can be called the structural and anatomical units of the placenta.

The number of cotyledons changes as the placenta matures. When it finally matures, the total number of such structural and anatomical formations is several dozen.

Fetal part of the placenta

Cotyledon

The main constituent of the placenta resembles a bowl in appearance. Each structural and anatomical unit of placental tissue has a large branch of the umbilical blood vessel, which branches into several small branches.

This structure provides a very important function of the placenta - the blood supply to the fetus's body with all the necessary substances for its growth and development. The plentiful circulatory system that covers the cotyledon provides blood flow to each individual site of the placental tissue. This helps to ensure uninterrupted blood flow not only to the placenta itself, but also to the body of an actively developing baby.

How is the blood supply ensured?

This question is very important, since the functioning of the placenta is impossible without uninterrupted blood flow. Nutrition of the uterus, in which the baby develops, is carried out through the ovarian and uterine arteries... It is their doctors who call it spiral vessels. The branches of the ovarian and uterine arteries are located in the intervillous space.

It is important to note that there is a pressure difference between the spiral vessels and the intervillous space. This feature is necessary in order for gas exchange and the provision of nutrients to occur. The difference in pressure contributes to the fact that the blood from the arteries penetrates to the villi, washes them and then moves to the chorionic plate. Then it enters the maternal veins.

This feature of the blood flow provides a certain permeability of the placental tissue. It is believed that the penetration capacity of various nutrients and oxygen gradually increases with each subsequent day of pregnancy. By 32-34 weeks, placental permeability is maximal. Then it begins to gradually decrease.

The weight

During pregnancy, the size of the placenta is almost constantly changing. So, for childbirth, a healthy placenta weighs on average about 0.5-0.6 kg. Its diameter in most cases is from 16 to 20 cm.

The thickness of the placenta can vary. It depends a lot on individual characteristics, as well as on whether there are any pathologies of the formation of this organ. With each subsequent day of pregnancy, the thickness of the placenta increases.

Doctors believe that such an increase ends only at 36-37 weeks of pregnancy. On average, after childbirth, the thickness of the normal placenta is approximately 2-4 cm.

Type of

Human placental tissue has a number of features that distinguish it from the placenta of other mammals. The human placenta is of the hemochorial type. This type of placental tissue is characterized by the possibility of maternal blood circulation around the villi, in which the fetal capillaries are located.

This structure of the placenta has interested many scientists. Already at the beginning of the 20th century, Soviet scientists conducted a number of scientific studies and made interesting developments based on the properties of placental tissue. So, Professor V.P. Filatov has developed special pharmaceutical preparations that contain in their chemical composition extract or suspension of the placenta.

Nowadays science has advanced greatly. Scientists have learned to actively work with the placenta. Stem cells are isolated from it, which have a number of important functions. There are even cord blood banks where they are stored. The storage of stem cells requires certain conditions and the responsible observance of a number of strict sanitary and hygienic rules.

For many years, scientists believed that the human hemochorial placenta was a sterile organ. However, numerous Scientific research rejected it. Even in a healthy placenta after childbirth, some microorganisms are found, many of which live in oral cavity in a pregnant woman.

How is it formed?

Placenta formation is a complex biological process. Scientists believe that the placenta is actively forming at 15-16 weeks of gestation. However, the term for the final development of an organ may vary. So, only at the 20th week of pregnancy, blood vessels begin to actively function in the placental tissue.

In most cases, the placenta forms in the back of the uterus. Placental tissue is formed with the participation of a special embryonic formation - cytotrophoblast and directly the endometrium itself (the inner lining of the uterine wall).

The final histological structure of the placenta became known to doctors relatively recently - in the era of microscopic examinations. In the placental tissue, scientists distinguish several sequentially located layers:

Decidua- the first layer in the direction from the uterus to the embryo. In fact, it is an altered endometrium.
Lanthans layer(Rohr's fibrinoid).
Trophoblast. This layer covers the lacunae and grows into the walls of the spiral arteries, which prevents their active contraction.
Numerous lacunae that are filled with blood.

Multi-core symplast lining cytotrophoblast (syncytiotrophoblast).
Cytotrophoblast layer... It is a layer of located cells that form syncytium and produce the formation of certain hormone-like substances.
Stroma... It is a connective tissue in which blood supply vessels pass. Also in this layer are very important cellular elements - Kashchenko-Hoffbauer cells, which are macrophages and provide local immunity.
Amnion. Participates in the subsequent formation of amniotic fluid. Needed to form a special aquatic environment, in which the intrauterine development of the baby will take place.

A very important structural element of the placenta is its basal decidua. It is a kind of barrier between the maternal and fetal part of the placenta. In the area of the basal decidua there are numerous depressions, inside of which maternal blood is present.

Functions

The placenta plays a very important role during pregnancy. The number of functions performed by this body is quite large. One of the most important of them is the protective or barrier function. The placenta is involved in the formation of the blood-placental barrier. It is necessary so that the intrauterine development of the fetus is not disturbed.

The following anatomical units are involved in the participation of the hematoplacental barrier:

the cell layer of the endometrium (the inner wall of the uterus);
basement membrane;
loose pericapillary connective tissue;
basement membrane of trophoblast;
cytotrophoblast cell layers;
syncytiotrophoblast.

Such a complex structure is necessary in order for the blood-placental barrier to provide important functions of the placenta. Violation of the histological structure can be dangerous. In such a situation, the placental tissue simply cannot fully function.

Participation in gas exchange

Through the blood vessels, which are in large numbers in the placental tissue, the fetus receives oxygen, and also "gets rid" of carbon dioxide.

This happens through the usual simple diffusion. At the same time, oxygen penetrates into the body of an actively growing baby, and waste carbon dioxide is released. Such a peculiar " cellular respiration"Occurs throughout the entire period of pregnancy. This unique mechanism develops due to the fact that the lungs of the fetus are formed quite late.

A child in the mother's womb does not breathe on its own. He will take his first breath only after birth. In order to compensate for this condition, such a cellular gas exchange takes place.

Providing food

Despite the fact that the baby has a certain date pregnancy, the mouth is formed, as well as the organs of the digestive system, he cannot yet take food on his own. All the nutrients that a child's body needs for its birth, it receives through the blood vessels. Proteins, fats and carbohydrates enter the baby's body through the arteries of his mother. In the same way, the baby receives water, vitamins and minerals.

This feature of fetal nutrition clearly explains why the diet of a pregnant woman is very important. For full intrauterine development of the fetus future mom must carefully monitor what food she consumes during the day.

It is very important that fresh fruits and vegetables, as well as high-quality sources of protein, are regularly present in the diet of a pregnant woman.

Isolation of unnecessary exchange products

Kidneys and excretory system fetuses begin to function late enough. While they are not yet well formed, the placenta comes to the rescue. Through the placental tissue, the metabolites that are unnecessary, exhausted by the child's body, are removed. Thus, the fetal body "gets rid" of excess urea, creatinine and other substances. This process takes place through active and passive transport.

Hormone synthesis

The hormonal function of the placenta is perhaps one of the most important. During pregnancy, the placental tissue is even an organ of internal secretion, as it is involved in the formation of biologically active substances.

One of them is the most important hormone of pregnancy - chorionic gonadotropin. It is essential for the normal course of pregnancy. This hormone ensures the correct functioning of the placenta, and also stimulates the formation of progesterone in the body of a pregnant woman. It is necessary during pregnancy in order to stimulate the growth of the endometrium and temporarily stop the maturation of new follicles in the ovaries.

Placental lactogen is also formed under the participation of the placenta. This hormone is necessary in order to prepare the mammary glands for the upcoming changes - lactation. Under the influence of the placenta, the formation of another hormone necessary during pregnancy occurs - prolactin. It is also necessary in order to prepare the mammary glands of the expectant mother for the upcoming lactation.

Scientists have found that placental tissue can synthesize some other hormones - testosterone, relaxin, serotonin and others. In addition to the active synthesis of hormones, placental tissue is also involved in the formation of hormone-like substances that are necessary for the normal course and development of pregnancy.

Fetal protection

This function of the placenta can be divided into several types. So, it can be mechanical and immune. Each of them is very important during the period of intrauterine development of the fetus.

Mechanical protection of the fetus implies the protection of the child's body from any environmental influences. Placental tissue is a very delicate structure. It is located in the immediate vicinity of the fetus. With various injuries, the placenta, as it were, "softens" the blow. This helps to reduce the risk of harm to the fetus.

The immune protective function of the placenta is that the placenta is involved in providing the child's body with maternal antibodies. These special substances ensure the immunity of the fetus throughout its intrauterine life in the womb.

Antibodies that enter the baby's body from his mother through the blood are immunoglobulins. Some of them calmly penetrate the placenta, getting into the child's body. Thus, the placenta helps to protect the baby from a number of bacterial and viral infections.

The ingestion of maternal antibodies also helps to prevent an immunological conflict between the mother and the fetus. In this case, the maternal organism does not perceive the fetus as an alien genetic object. This feature helps to prevent rejection of the fetus from the uterine cavity throughout pregnancy.

It should be noted about the special role of syncytium - a special element of placental tissue. He participates in the absorption of a number of dangerous chemical substances that can cross the placenta from mother to fetus. Thus, the placenta, as it were, protects the baby's body from the penetration of dangerous drugs, toxic and other dangerous drugs into it.

It is important to remember that this selectivity of penetration can be individual. If the histological structure of the placenta is normal, then hazardous substances are retained. If it is violated, then toxins and poisons can easily penetrate into the child's body, causing irreparable harm to it. That is why doctors recommend that expectant mothers give up all bad habits during pregnancy.

Smoking and consumption of alcohol, as well as drugs can cause the development dangerous diseases active developing fetus... Preventing their development is much easier than trying to cope with the pathologies that have arisen in the future.

Maintaining healthy way life of the expectant mother is of great importance in the formation and normal functioning of the placenta.

Migration

The initial position of the placenta in the uterine cavity is a very important clinical indicator. Even the course of pregnancy depends on how it will be located.

Usually, placental tissue is attached to the back or front of the uterus. It is extremely rare that it is attached only to one of the side walls. The laying of placental tissue begins in the first trimester of pregnancy and is associated with the site of implantation of a fertilized egg.

Normally, a fertilized egg is attached to the fundus of the uterus. In this zone, there is good blood flow, which is necessary for the full intrauterine development of the fetus throughout pregnancy. However, this situation does not always develop.

Placenta on the anterior wall of the uterus

In obstetric practice, cases are recorded when the implantation of a fertilized egg occurs in the lower parts of the uterus. This is preceded by a huge variety of reasons. In this case, the fertilized egg can descend almost to the base of the internal uterine pharynx, where it attaches to the uterine wall.

The lower the implantation occurs, the lower the placenta is. The accretion of placental tissue on the area of the internal uterine pharynx is called presentation by doctors. This dangerous pathology significantly worsens the course of pregnancy and can even cause the development of dangerous complications.

Low placentation

The original location of the placental tissue may change. This most often occurs when the placenta is attached to the anterior wall of the uterus. The process of changing the initial localization of placental tissue is called migration. The displacement of the placenta in this case, as a rule, occurs from bottom to top. Thus, if the low position of the placental tissue was detected in the first half of pregnancy, then it may still change.

Usually, the placenta migration process proceeds rather slowly - within 6-10 weeks. It ends completely, as a rule, only by the middle of the 3rd trimester of pregnancy.

The placenta, located on the back wall of the uterus, practically does not migrate. The likelihood of displacement of the placental tissue in this position is extremely small. This is largely facilitated by certain structural features of the uterus.

Ultrasound: 12 weeks, 4 days. Placenta on the anterior wall, complete placenta previa

Norm

A healthy placenta is an important part of a healthy pregnancy. The development of this unique organ of pregnancy occurs gradually. From the moment of formation in the female body to childbirth, the placenta is almost constantly changing.

Doctors can evaluate the anatomical properties of the placenta, as well as identify various anomalies in its development by performing ultrasound examinations. To do this, throughout the pregnancy, the expectant mother must undergo several ultrasounds.

With the help of modern devices, specialists can get a fairly clear visualization of the placental tissue. During an ultrasound examination, the doctor can see the structure of the placenta, the presence of any diffuse changes in it, as well as emerging pathologies.

A very important clinical indicator, which is necessarily determined by obstetricians-gynecologists during pregnancy, is the maturity of the placenta. At each stage of pregnancy, it changes. It's quite normal. In this case, it is important to assess the correspondence of the maturity of the placenta to a certain period of pregnancy.

So, experts identify several options for the maturity of the placental tissue:

Zero (0). Characterizes the normal structure of the placenta until approximately 30 weeks of gestation. The placenta of this maturity has a fairly smooth and even surface.
First (1)... It is characteristic of a healthy placenta between 30 and 34 weeks of gestation. At maturity of the first degree, specific inclusions appear on the placenta.
Second (2). Forms normally after 34 weeks of gestation. Such placental tissue looks more prominent, specific striation appears on it, as well as small grooves.
Third (3). It is the norm for normal full-term pregnancies. The placenta, which has such a degree of maturity, has rather pronounced large waves on its surface, which reach the basal layer. Also, on the outer surface of the placental tissue, spots merging with each other appear, having irregular shape- salt deposits.

Determining the degree of maturity of the placenta allows doctors to orientate themselves in the timing of the upcoming birth. In some cases, the placental tissue matures too quickly. This leads to the development of a number of dangerous complications. In this case, the tactics of pregnancy must be reviewed by specialists.

Pathology

Unfortunately, abnormalities in the development and formation of the placenta are quite common in obstetric practice. Such conditions significantly worsen the prognosis of the course of pregnancy. The resulting defects in the structure of the placenta also contribute to the deterioration of blood flow, which is necessary for the full intrauterine development of the baby.

Currently, quite a few different pathologies of the placenta are known. One of the most dangerous of them is the strong accretion of placental tissue to the uterine wall. It would seem that the stronger the placenta "grows" into the endometrium, the more reliable the fixation should be, but in fact this is not entirely true.

Strong accretion of the placenta to the uterine wall is dangerous for the development of problems with its separation during childbirth. In such a situation, the birth of the child, as a rule, proceeds normally, and the birth of the placenta is delayed. Such a clinical situation can be dangerous by the development of massive uterine bleeding.

Also, the long-term presence of the placenta in the uterine cavity is a threat to the development of infection of the reproductive organs.

With a strong increment of placental tissue to the wall of the uterus, surgical gynecological intervention is required. In this situation, doctors purposefully separate the placenta from the uterine walls.

Quite often, scars form on the uterus. This usually happens when various surgical operations- cesarean section, excision of damaged tissues and others. A strong proliferation of connective tissue leads to scarring.

The ingrowth of the placenta into a scar on the uterus is quite dangerous pathology... In this case, during natural childbirth may arise dangerous complications... In order to avoid them, doctors are often forced to resort to performing surgical obstetrics - cesarean section.

Strong prolapse of the placenta to the level of the internal uterine pharynx is dangerous by the development of its presentation. This pathology worsens the prognosis of gestation. With placenta previa, the threat of developing dangerous infectious diseases and premature birth is quite high. In order to preserve and prolong pregnancy as much as possible, the expectant mother must strictly follow the recommendations made for her by doctors.

Placental abruption is another dangerous pathology that occurs in obstetric practice. It is characterized by detachment of placental tissue due to certain reasons from the walls of the uterus. In this case, bleeding usually develops. If placental abruption occurs over a fairly large area, then this situation is extremely dangerous for the life of the fetus. Massive detachment of placental tissue, accompanied by the appearance functional disorders in a child's body, it may become an indication for an emergency caesarean section.

Another dangerous pathology is placental edema. A variety of reasons can lead to the development of this condition, including bacterial and viral infections. Prolonged edema of the placenta can lead to the development of placental insufficiency, fetal hypoxia, and also provoke premature birth. When this pathology is detected, doctors carry out complex treatment.

If the breaks in the placental tissue are quite significant, then this will contribute to the disruption of its functioning. In this case, the general condition of the fetus may also be disturbed. Violation of the blood supply can affect the increase in heart rate of the baby, as well as the increase in oxygen deficiency in his blood.

It is possible to detect defects and small hemorrhages in the placenta only with the help of modern ultrasound examinations. Minor injuries, as a rule, are determined already retrospectively - after childbirth during a visual examination of the placenta.

Define structural changes it is possible with the help of histological examination, which is performed after childbirth. For this examination, the placenta is sent to a special laboratory, where it is studied.

For what the placenta is, see next video Larisa Sviridova.

There are two surfaces of the placenta: the fruit, facing the fetus, and the mother, adjacent to the wall of the uterus. The fruit surface is covered with amnion - a smooth, shiny grayish shell, the umbilical cord is attached to its central part, from which the vessels radiate radially. Maternal surface of the placenta dark brown, divided into 15-20 lobules - cotyledons, which are separated from each other by placental septa. From the umbilical arteries, fetal blood enters the villous vessels (fetal capillaries), carbon dioxide from the fetal blood passes into the maternal blood, and oxygen from the maternal blood passes into the fetal capillaries. Oxygenated fetal blood from the cotyledons collects to the center of the placenta and then enters the umbilical vein. Maternal and fetal blood do not mix, there is a placental barrier between them. The structure of the placenta is finally formed by the end of the first trimester, but its structure changes as the needs of the growing baby change. From the 22nd to 36th weeks of pregnancy, an increase in the mass of the placenta occurs, and by the 36th week it reaches full functional maturity. Normal placenta by the end of pregnancy it has a diameter of 15-18 cm and a thickness of 2 to 4 cm. After childbirth (the placenta, together with the membranes of the fetus - the afterbirth - is normally born within 15 minutes after the birth of the child), the placenta must be examined by the doctor who delivered the child. Firstly, it is very important to make sure that the placenta was born as a whole (that is, there is no damage on its surface, and there is no reason to believe that pieces of the placenta remained in the uterine cavity). Secondly, according to the state of the placenta, one can judge the course of pregnancy (whether there was a detachment, infectious processes, etc.). There are three degrees of maturity of the placenta. Normally, up to 30 weeks of pregnancy, the zero degree of maturity of the placenta should be determined. The first degree is considered acceptable from the 27th to the 34th week. The second is from 34th to 39th. Starting from the 37th week, the third degree of maturity of the placenta can be determined. At the end of pregnancy, the so-called physiological aging of the placenta occurs, accompanied by a decrease in the area of its exchange surface, the appearance of areas of salt deposition. According to the ultrasound data, the doctor determines the degree of maturity of the placenta, assessing its thickness and structure. Depending on the correspondence between the gestational age and the degree of maturity of the placenta, the doctor chooses the tactics of pregnancy management. This information also affects the tactics of delivery.

The mature placenta is a disc-shaped structure with a diameter of 15-20 cm and a thickness of 2.5 - 3.5 cm. Its mass reaches 500-600 grams. The maternal surface of the placenta, which faces the wall of the uterus, has a rough surface formed by the structures of the basal part of the decidua. The fruiting surface of the placenta, which faces the fetus, is covered with an amniotic membrane. Under it are visible vessels that go from the place of attachment of the umbilical cord to the edge of the placenta. The structure of the fruiting part of the placenta is represented by numerous chorionic villi, which are combined into structural formations - cotyledons. Each cotyledon is formed by a bifurcated stem villi containing fetal vessels. The central part of the cotyledon forms a cavity that is surrounded by many villi. In a mature placenta, there are from 30 to 50 cotyledons. Placental cotyledon is conditionally comparable to a tree, in which the 1st order supporting villi is its trunk, the 2nd and 3rd order villi are large and small branches, the intermediate villi are small branches, and the terminal villi are leaves. Cotyledons are separated from each other by septa (septa) emanating from the basal plate.

Placenta functions

Its functions are multifaceted and are aimed at maintaining pregnancy and the normal development of the fetus. Gas exchange is carried out through the placenta: oxygen penetrates from the maternal blood to the fetus, and carbon dioxide is transported in the opposite direction. The respiratory function of the placenta is carried out by transferring oxygen from the maternal to the fetal blood and carbon dioxide from the fetal to the maternal blood, depending on the needs of the fetus. The fetus receives nutrients through the placenta and gets rid of its waste products. The placenta has immune properties, that is, it allows the mother's antibodies (protective proteins) to pass to the child, ensuring his protection, and at the same time detains cells immune system mothers who, having penetrated the fetus and recognizing a foreign object in it, could trigger the rejection of the fetus, She plays the role of an endocrine gland and synthesizes hormones. Placental hormones (chorionic gonadotropin, placental lactogen, progesterone, estrogens, etc.) ensure the normal course of pregnancy, regulate the most important vital functions of the pregnant woman and the fetus, and participate in the development of labor. The activity of metabolic processes in the placenta is especially high in the third trimester of pregnancy.

In addition, the placenta has a protective function. In it, with the help of enzymes, the harmful substances formed both in the body of the mother and in the body of the fetus are destroyed. The barrier function of the placenta depends on its permeability. The degree and rate of transition of substances through it are determined by various factors. With a number of complications of pregnancy, various diseases carried by pregnant women, the placenta becomes more permeable to harmful substances than with a normal pregnancy. In this case, the risk increases sharply intrauterine pathology fetus, and the outcome of pregnancy and childbirth, the condition of the fetus and the newborn depend on the degree and duration of the damaging factor and on the safety of the protective function of the placenta. With the normal development of pregnancy, there is a relationship between the growth of the fetus, its body weight and the size, thickness, weight of the placenta. Until 16 weeks of gestation, the development of the placenta outstrips the growth rate of the fetus. In the event of the death of the embryo (fetus), the growth and development of chorionic villi is inhibited and the involutional-dystrophic processes in the placenta progress. Having reached the necessary maturity at 38-40 weeks of pregnancy, the processes of formation of new vessels and villi stop in the placenta.

During pregnancy, the mother's body adapts to the fetus, which distinguishes the functional mother-fetus system from the life forms of two organisms known in biology. A strict sequence of not only the development of organs and systems of the fetus is genetically programmed, but also the processes of adaptation to pregnancy of the maternal organism, which occurs in full accordance with the stages of intrauterine development.

For example, the receipt of oxygen from the outside is provided by the hemodynamic functional system mother - placenta - fetus, which is a subsystem of the general functional system mother - fetus. It develops first in the earliest ontogeny. In it, fetoplacental and uteroplacental blood circulation is simultaneously formed.

In the placenta, there are two blood flows: 1) the flow of maternal blood, due mainly to the systemic hemodynamics of the mother; 2) the blood flow of the fetus, depending on the reactions of its cardiovascular system. The maternal blood flow is shunted by the vascular bed of the myometrium. At the end of pregnancy, the percentage of blood flowing to the intervillous space varies between 60 and 90. These fluctuations in blood flow depend mainly on the tone of the myometrium. A paravascular network develops around the arteries and veins in the villi, which is considered as a shunt capable of passing blood in conditions when blood flow through the exchangeable part of the placenta is obstructed. Fetoplacental and uteroplacental blood circulation are coupled, the intensity of blood flow is the same. Depending on the changes in the state of activity of the mother and the fetus, each of them redistributes blood in such a way that the oxygenation of the fetus remains within the normal range.

The development of the endocrine functional system of the fetus - placenta - mother is peculiar, which is especially clearly seen in the example of estriol synthesis. The enzyme systems required for estrogen production are distributed between the fetus (its adrenal glands and liver), the placenta, and the mother's adrenal glands. The first step in estrogen biosynthesis during pregnancy (hydroxylation of the cholesterol molecule) occurs in the placenta. The resulting pregnenolone from the placenta enters the fetal adrenal glands, converting them into dehydroepiandrosterone (DEA). DEA enters the placenta with venous blood, where, under the influence enzyme systems undergoes aromatization and turns into estrone and estradiol. After a complex hormonal exchange between the body of the mother and the fetus, they are converted into estriol (the main estrogen of the fetoplacental complex).

The placenta (from Lat. Placenta- "cake"), or baby's place, is an organ that develops in the uterus during pregnancy, which communicates between the mother's body and the fetus. Complex biological processes take place in the placenta that ensure the normal development of the embryo and fetus, gas exchange, hormone synthesis, protection of the fetus from harmful factors, immune regulation, etc. After fertilization, a cavity or lacuna is formed in the uterine wall, filled with maternal blood, in which the embryo is located by obtaining nutrients directly from the tissues of the mother's body. The trophoblast cells surrounding the embryo divide intensively, forming a kind of branched membrane around the embryo, "penetrated" by lacunae. The vessels of the embryo grow into each branch of this shell. As a result, an exchange is established between the mother's blood, which fills the lacunae, and the blood of the embryo. This is the beginning of the formation of the placenta - an organ equally "belonging" to both mother and baby. After the birth of the fetus, the placenta is rejected from the uterine cavity.

Placenta structure

There are two surfaces of the placenta: the fruit, facing the fetus, and the mother, adjacent to the wall of the uterus. The fruit surface is covered with amnion - a smooth, shiny grayish shell, the umbilical cord is attached to its central part, from which the vessels radiate radially. The maternal surface of the placenta is dark brown, divided into 15-20 lobules - cotyledons, which are separated from each other by placental septa. From the umbilical arteries, fetal blood enters the villous vessels (fetal capillaries), carbon dioxide from the fetal blood passes into the maternal blood, and oxygen from the maternal blood passes into the fetal capillaries. Oxygenated fetal blood from the cotyledons collects to the center of the placenta and then enters the umbilical vein. Maternal and fetal blood do not mix, there is a placental barrier between them. The structure of the placenta is finally formed by the end of the first trimester, but its structure changes as the needs of the growing baby change. From the 22nd to 36th weeks of pregnancy, an increase in the mass of the placenta occurs, and by the 36th week it reaches full functional maturity. The normal placenta by the end of pregnancy has a diameter of 15-18 cm and a thickness of 2 to 4 cm.After childbirth (the placenta, together with the membranes of the fetus - the afterbirth - is normally born within 15 minutes after the birth of the child), the placenta must be examined by the doctor who took the birth ... Firstly, it is very important to make sure that the placenta was born as a whole (that is, there is no damage on its surface, there is no reason to believe that the pieces of the placenta remained in the uterine cavity). Secondly, according to the state of the placenta, one can judge the course of pregnancy (whether there was a detachment, infectious processes, etc.). There are three degrees of maturity of the placenta. Normally, up to 30 weeks of pregnancy, the zero degree of maturity of the placenta should be determined. The first degree is considered acceptable from the 27th to the 34th week. The second is from 34th to 39th. Starting from the 37th week, the third degree of maturity of the placenta can be determined. At the end of pregnancy, the so-called physiological aging of the placenta occurs, accompanied by a decrease in the area of its exchange surface, the appearance of areas of salt deposition. According to the ultrasound data, the doctor determines the degree of maturity of the placenta, assessing its thickness and structure. Depending on the correspondence between the gestational age and the degree of maturity of the placenta, the doctor chooses the tactics of pregnancy management. This information also affects the tactics of delivery.

Placenta functions

Its functions are multifaceted and are aimed at maintaining pregnancy and the normal development of the fetus. Gas exchange is carried out through the placenta: oxygen penetrates from the maternal blood to the fetus, and carbon dioxide is transported in the opposite direction. Respiratory the function of the placenta is carried out by transferring oxygen from the maternal to the fetal blood and carbon dioxide from the fetal to the maternal blood, depending on the needs of the fetus. The fetus receives nutrients through the placenta and gets rid of its waste products. The placenta has immune properties, that is, it passes the mother's antibodies (protective proteins) to the child, ensuring his protection, and at the same time detains the cells of the mother's immune system, which, having penetrated the fetus and recognizing a foreign object in it, could trigger fetal rejection reactions. plays the role of an endocrine gland and synthesizes hormones. Placental hormones (chorionic gonadotropin, placental lactogen, progesterone, estrogens, etc.) ensure the normal course of pregnancy, regulate the most important vital functions of the pregnant woman and the fetus, and participate in the development of labor. The activity of metabolic processes in the placenta is especially high in the third trimester of pregnancy.

In addition, the placenta performs protective function. In it, with the help of enzymes, the harmful substances formed both in the body of the mother and in the body of the fetus are destroyed. Barrier the function of the placenta depends on its permeability. The degree and rate of transition of substances through it are determined by various factors. With a number of complications of pregnancy, various diseases carried by pregnant women, the placenta becomes more permeable to harmful substances than with a normal pregnancy. In this case, the risk of intrauterine pathology of the fetus sharply increases, and the outcome of pregnancy and childbirth, the condition of the fetus and the newborn depend on the degree and duration of the action of the damaging factor and on the preservation of the protective function of the placenta.

Where is the placenta located? With a normal pregnancy, the placenta is located most often in the mucous membrane of the anterior or posterior wall of the uterus. The location of the placenta is determined using ultrasound. The thickness of the placenta grows continuously up to 36-37 weeks of pregnancy (by this time it ranges from 2 to 4 cm). Then its growth stops, and in the future, the thickness of the placenta either decreases or remains at the same level.

Low attachment of the placenta. In the early stages of pregnancy, the placenta often reaches the internal uterine pharynx - the exit from the uterus, but in most women, in the future, with the growth of the uterus, it rises up. Only in 5% the low position of the placenta remains until the 32nd week, and only in a third of these 5% the placenta remains in this position by the 37th week. With a low location of the placenta, doctors decide on the method of delivery, because in this situation, placental abruption can occur before the birth of the fetus, and this is dangerous for the mother and baby.

Placenta previa. If the placenta reaches the internal pharynx or overlaps it, they speak of placenta previa. It most often occurs in re-pregnant women, especially after previous abortions and postpartum diseases (this damages the inner layer of the uterus, the placenta attaches to the intact area). In addition, tumors and abnormalities of the uterus contribute to placenta previa. Ultrasound determination of placenta previa in early dates pregnancy may not be confirmed later. However, such an arrangement of the placenta can provoke bleeding and even premature birth. This situation is necessarily monitored over time by ultrasound, i.e. with an interval of 3-4 weeks, and always before childbirth.

Placenta accreta. Chorionic villi during the formation of the placenta "penetrate" into the lining of the uterus (endometrium). This is the same membrane that is rejected during menstrual bleeding - without any damage to the uterus and to the body as a whole. However, there are times when the villi grow into the muscle layer, and sometimes into the entire thickness of the uterine wall. This situation is extremely rare, it threatens the development of bleeding after the birth of the fetus, which can be stopped only by surgery, when the placenta has to be removed along with the uterus.

Dense attachment of the placenta. In fact, the dense attachment of the placenta differs from the increment in the shallower depth of germination of the chorionic villi into the wall of the uterus. In the same way as placenta accreta, tight attachment often accompanies presentation or low position of the placenta.Unfortunately, it is possible to recognize accretion and tight attachment of the placenta (and distinguish them from each other) only during childbirth. In the case of a tight attachment, they resort to manual separation of the placenta - the doctor taking delivery, inserts his hand into the uterine cavity and separates the placenta.

Placental abruption. As noted above, placental abruption can accompany the first stage of labor when the placenta is low or occur during pregnancy with placenta previa. In addition, there are cases when a premature detachment of a normally located placenta occurs. This is a severe obstetric pathology that occurs in 1-3 out of a thousand pregnant women,

With this complication, the woman is necessarily hospitalized. Manifestations of placental abruption depend on the area of the detachment, the presence, size and rate of bleeding, the reaction of the woman's body to blood loss. Small detachments may not manifest themselves in any way and are detected after childbirth when examining the placenta.If placental abruption is insignificant, its symptoms are mild, in general fetal bladder in childbirth, it is opened, which slows down or stops placental abruption. Severe clinical picture and increasing symptoms internal bleeding(increased heart rate, decreased blood pressure, fainting, pain in the uterus) are indications for caesarean section(in rare cases, you even have to resort to removing the uterus - if it is soaked in blood and does not respond to attempts to stimulate its contraction).

Change in the thickness and size of the placenta

Depending on the pathology of pregnancy, the failure of the placenta function during its excessively early maturation is manifested by a decrease or increase in the thickness of the placenta. So "Thin" placenta(less than 20 mm in the third trimester of pregnancy) is characteristic of gestosis (a complication that is more often manifested by an increase in blood pressure, the appearance of edema, protein in the urine), the threat of termination of pregnancy, malnutrition (growth retardation) of the fetus, while in hemolytic disease (when in the body of a Rh-negative pregnant woman, antibodies to Rh-positive erythrocytes of the fetus are produced, the erythrocytes of the fetus are destroyed) and diabetes mellitus the "thick" placenta (50 mm or more) testifies to placental insufficiency. Thinning or thickening of the placenta indicates the need for treatment measures and requires repeated ultrasound examination.

Reducing the size of the placenta- in this case, its thickness can be normal, and the area is reduced. There are two groups of reasons leading to a decrease in the size of the placenta. Firstly, it can be a consequence of genetic disorders, which is often combined with fetal malformations (for example, Down's syndrome). Secondly, the placenta may "fall short" in size due to the influence of various unfavorable factors (severe preeclampsia in the second half of pregnancy, increased blood pressure, as well as genital infantilism - underdevelopment, the small size of a woman's genitals, which ultimately leads to a decrease in blood flow in the vessels of the placenta and to its premature maturation and aging). In either case, the "small" placenta cannot cope with the responsibilities assigned to it of supplying the baby with oxygen and nutrients and getting rid of metabolic products. The fetus lags behind in development, does not gain weight, and after birth, the baby recovers for a long time to achieve normal age indicators... Timely treatment of the pathologies that have arisen can significantly reduce the risk of fetal underdevelopment.

An increase in the size of the placenta. Placental hyperplasia occurs in Rh-conflict, severe anemia (decreased hemoglobin amount), diabetes mellitus, syphilis and other infectious lesions of the placenta during pregnancy (for example, with toxoplasmosis), etc. Various infectious diseases transferred during pregnancy also significantly affect the placenta and amniotic fluid. It makes little sense to list all the reasons for the increase in the size of the placenta, however, it must be borne in mind that when this condition is detected, it is very important to establish the cause, since it is it that determines the treatment.Therefore, one should not neglect the studies prescribed by the doctor, because the placental hyperplasia is the result of placental hyperplasia. failure leading to intrauterine growth retardation.

Developmental abnormalities, dystrophic and inflammatory changes in the placenta can lead to placental insufficiency. This condition on the part of the placenta is manifested in the lag of the fetus from the gestational age, lack of oxygen and nutrients. The child is more difficult to endure the birth itself, since during this period he suffers from a deficiency of oxygen and nutrients. Placental insufficiency is diagnosed using ultrasound and CTG (cardiotocography) and dopplerometry (the state of blood flow in the vessels). Therapy of this pathology is carried out with the help of drugs that improve uteroplacental blood flow, nutrient solutions and vitamins.

Placental integrity

A few minutes after the birth of the child, sequential contractions begin: the entire musculature of the uterus contracts, including the area of attachment of the placenta, which is called the placental site. The placenta does not have the ability to contract, so it is displaced from the place of attachment. With each contraction, the placental area decreases, the placenta forms folds protruding into the uterine cavity, and, finally, exfoliates from its wall. Disruption of the connection between the placenta and the wall of the uterus is accompanied by a rupture of the uteroplacental vessels in the region of the detached site of the placenta. Blood flowing from the vessels accumulates between the placenta and the uterine wall and contributes to the further separation of the placenta from the attachment site. Usually, the membranes with the placenta are born after the birth of the child. There is such an expression: “born in a shirt,” so they say about a happy person. If during childbirth there was no rupture of the membranes, which is extremely rare, then the child is born in fetal membrane- "shirt". If you do not free the baby from it, he will not be able to breathe on his own and may die.

After the release of the placenta from the uterine cavity, the placenta is carefully examined, measured, weighed, and, if necessary, carry out its histological examination. If there is any doubt that the placenta or membranes have completely separated, a manual check of the uterine cavity is performed, since parts of the placenta remaining in the uterus can cause bleeding and inflammation. This manipulation is performed under general anesthesia.

Thanks to modern methods studies, features of the structure, functioning and location of the placenta can be detected in a timely manner and effectively treated. This is possible if the expectant mother will undergo all the necessary examinations.