Development stages of the human embryo. Development of the embryo by day from conception. Intrauterine development of the child
The birth of a child into the world is a very complex and responsible process. Every mom-to-be wants to know how the embryo develops week by week. After all, this action is reliably hidden from human eyes, but it has been carefully studied by scientists.
So, the development of the embryo by week
The first few hours after conception. The sperm cell enters the egg and the fertilization process takes place. Up to eight weeks, the resulting fetus is called an "embryo".
1-2 weeks... There is an active embryo moves along the fallopian tube, enters the uterus and by the end of the second week is fixed on its mucous membrane. already at this stage, and it depends on the set of chromosomes that the sperm contained that fertilized the egg.
3-4 weeks... Despite the fact that the fetus is very tiny, his heart is already beginning to throb. The nervous system, bone and muscle, is gradually emerging. As a rule, during this period, a woman begins to guess about her pregnancy, since there is no menstruation.
5th week... The embryo is about 6-9 millimeters long. His brain and spinal cord are already developing, the formation of the central nervous system is taking place. The heart becomes detached, arms, legs, a head with holes for the eyes, mouth and nose appear.
7th week... The embryo is already 12 millimeters long and weighs 1 gram. The fetus has its own and begins to move, however, due to its tiny size, the woman does not feel the movement in any way.
8th week... pregnancy proceeds dynamically and systematically. The body is already formed in the embryo. You can distinguish the face, nose, ears. The nervous system continues to improve and the skeleton continues to grow. The first rudiments of the genital organs appear.
9th week... The whole body of the baby is already sensitive. He can touch himself, the umbilical cord.
10-13 weeks... This stage is one of the most important in the process, since the nervous system and most organs are actively developing. The fetus begins to make the first swallowing movements. As a result of the active development of the skeleton, its size is rapidly increasing, which entails the growth of the pregnant woman's tummy. During this period, the baby already hears, the vocal cords are formed.
17-20 weeks... Photos of the embryo by week during this period show that all parts of the body are already clearly visible. The kid opens his mouth, blinks. Due to the fact that its dimensions already exceed 14 centimeters, the expectant mother begins to feel light jolts.
21-25 weeks... The weight of the fetus is rapidly increasing, the first fatty deposits appear. The baby's lungs are quite developed, and in the case of his premature birth after 23 weeks, there is a great chance of survival with intensive care. The heartbeat of the child begins to be heard if you put your ear to the belly of a pregnant woman.
26-30 weeks... The development of the embryo week by week during this period is very active. So, a sucking reflex is formed, the first hairs on the head and eyelashes may appear, nails grow.
31-35 weeks. The baby's skin becomes thicker. During wakefulness, he opens his eyes, in a dream he closes. The brain is actively developing, the number of convolutions is increasing. The lungs are fully formed, the grasping reflex develops.
36-40 weeks... The period of waiting and preparation for childbirth. From this moment on, one can expect the first contractions - the harbingers. the cervix is shortened. The body prepares for childbirth. At this stage, the development of the embryo is completed week by week. The kid calms down, pushes less, because, due to the significant size, it becomes cramped for him. From 38 weeks, the baby is considered full-term.
From the moment of conception to the birth of a child, two cells in the beginning give rise to a colossal number of unique processes. Any future mother is interested in knowing what is going on inside her, how the fetus is formed. And the mother who resorted to eco and even more so. Therefore, women always want to carefully study the development of the embryo by day after transfer in order to visualize the desired result as accurately as possible.
Embryo cultivation
After the union of the gametes of the spouses (egg and sperm), a new life begins to emerge. The unique creation process thanks to scientists is available under a microscope. The development of the embryo every day before transfer takes place in a special environment - a Petri dish. The process takes 3 to 5 days, depending on when the embryo transfer is scheduled. After replanting, the uterine stage of fetal formation already begins.
12-16 hours after the union of male and female cells, the first assessment of the unborn child is carried out. The initial development of oocytes after IVF fertilization is very important. At this stage, the formation of the future karyotype begins - a bond of chromosomes is formed, which are responsible for all processes in the body, and gender is established.
In medicine, all stages of fetal formation have names - zygote, morula, blastocyst, gastrula, embryo, fetus. The developmental stages of embryos after transfer by day begin with a morula or blastocyst. It depends on what day the transfer was made.
Zygote. Division is a key element of any life. On the second day, the fertilized egg begins to divide into 2-4 cells, by the third day there are 6-8 cells. The cells into which the embryo is divided are called blastomeres.
The analysis of development at this stage is determined by the following factors:
- the total number of blastomeres;
- number without nuclei (anuclear blastomeres);
- their shape and size are evaluated.
The first embryo labeling is carried out. The letters (A-B-C-D) indicate the quality, and the numbers indicate the number of blastomeres. For example, 4A is an embryo of excellent quality, with 4 blastomeres, 6D is a six-cell embryo of poor quality (anuclear blastomeres are more than 50%).
Development after transfer
Morula. By the end of the third day, most embryos with genetic damage stop developing. This happens because up to this point, the formation took place due to the nutrients of the egg itself, then the genetic apparatus is launched and the embryo behaves according to the program of natural selection. Surviving embryos continue to divide, the number of blastomeres reaches 10-16.
The process of compaction is started - intercellular connections are strengthened, the cell surface is smoothed. The next stage of quality assessment is carried out. If there are risks of stopping development at the morula stage, a decision is made about the possibility of transferring it to the uterus. It is generally accepted that in a woman's body, the chances of survival increase.
The development of 3 day old embryos after replanting normally does not differ from if they continued to be cultured in the medium.
On the 4th day from the moment of fertilization, the compaction process is completed, the blastomeres are divided into two groups - cell mass and trophoblast. The first of them will give development to all organs and tissues, from the other extraembryonic membranes will form - chorion, amnion, allantois, yolk sac, trophoblast will also play a decisive role at the time of implantation.
Blastocyst. A cavity appears inside the morula at the moment of division of blastomeres into groups. When it reaches half its size, the embryo is already called a blastocyst. The chances of survival are higher in those blastocysts in which the cavity is larger and both groups of blastomeres are better formed.
Then the development of a 5-day-old embryo continues according to the scheme - the cavity increases, the transparent membrane stretches and breaks (hatching). The blastocyst is now ready for implantation. A transplant into the uterus is performed. Further, the development of the embryo begins by days after the transfer of 5 days.
Gastrula. On the 6-7th day after fertilization of the egg, or on 3-4 DPP of 3 days, or on 1-2 DPP of 5 days, the implantation process begins. The blastocyst adheres to the mucous membrane, the trophoblast begins to form villi, which help to penetrate deeper into the endometrium.
Closer to the 9th day of the PO, the implantation process completely ends, the embryo is completely immersed in the uterus. Further, a complex mechanism of placenta formation is launched, the formation of future organs of the embryo, extraembryonic membranes, and the production of the hCG hormone begins. Every day, its level increases and on the 14th day after fertilization, pregnancy can sometimes be diagnosed. Now the embryo is fully called an embryo.
Important information for fetal development
What happens to the embryo after transfer to the uterus by day? In the absence of negative factors, the embryo develops safely every day. If at any stage there are deviations in the genome, the influence of the artificial environment for cultivation affects or there are processes in the woman's body that prevent its growth, then the chances of survival are small, “natural selection” takes place in the uterus.
How does the embryo develop after transfer to the uterus by day? If a 3-day-old embryo was implanted, then it is logical that it, first of all, reaches the blastocyst stage. After that, the development of the embryo after transfer to the uterus by day has the same scheme for everyone.
Why don't embryos develop after transfer? Among the reasons that stop the growth of embryos in the uterus, there may be the unwillingness of the endometrium to accept a foreign body, various endocrine, immune and other problems of the patient. Unfavorable factors are also stressful situations that lead to tachycardia.
Such a rapid heartbeat after embryo transfer may also be due to complications with the ovaries, which will also negatively affect implantation. But, the most likely problem is in the quality of the embryos themselves, on average, this is 80% of all failures.
To eliminate the risks of obtaining a low-quality embryo even at the stage of pregnancy planning, modern trends in genetics in in vitro fertilization are used. Genetic testing of parents of different levels (the whole genome or several genes) will determine the risk of getting pathologies of the unborn child, not only after birth, but also those that may appear with age. And the method of PGD - preimplantation genetic diagnosis, will determine deviations in the set of chromosomes before embryotransfer.
As scary as it may seem, in vitro fertilization works. Many women are happier after testing positive for hCG. And they are looking forward to the time of the ultrasound scan to confirm the onset of pregnancy and in order to hear their child for the first time.
Which heartbeat is heard? The first ultrasound after the analysis of hCG is scheduled for 21-24 DPP. As a rule, only the presence of the ovum, the place of its attachment, is determined by it. And only on the next ultrasound study, after a week and a half, an average of 35 dp can be seen in the heartbeat.
Further development of the fetus can also end in different ways. Basically, after the positive results of the first ultrasound, a woman diagnosed with pregnancy after IVF is observed, like any other. At this stage, the options for the course of pregnancy are the same.
Pregnancy is an important stage in every woman's life. Tenderness and awe evokes the understanding that a new life is growing inside you, a little man. The development of the embryo and fetus should be monitored not only by the doctor, but also by the woman herself. To make it more convenient to do this, you need to familiarize yourself with the stages of intrauterine growth of the baby.
Stages of fetal development
Pregnancy is a natural physiological process that occurs after the fertilization of an egg by a male sperm. As a result of this, a new organism is born - the embryo. On average, 40 weeks or 10 obstetric months pass from conception to delivery.
During this time, several stages of embryo development occur inside the womb. From a defenseless single-celled creature, he grows to a full-fledged man who can live independently. Pregnancy is divided into periods: embryonic and fetal.
At the first stage, the embryo acquires features characteristic of a person, and at the second stage, its organs and vital systems are formed. We propose to consider in more detail these stages of embryo development.
The embryonic period
Fertilization takes place in the fallopian tube. From this moment and the next 5 days, the cells in the ovum will divide exponentially, going down the tube into the uterine cavity. At the end of the path, this multicellular creature becomes like a blackberry. At this stage, it is called morula. By the end of the first week of pregnancy, it penetrates into the walls of the uterus and "connects" to the mother's circulatory system.
The next 7 days, the placenta, umbilical cord and neural tube are born, from which the nervous system of the fetus will form. From 14 to 21 days are critical. During this period, all the vital organs of the child, the rudiments of the nervous, circulatory, respiratory and digestive systems begin to be laid. A wide plate is formed in the head area, then the brain will form in this place. On the 21st day, the heart will begin to beat.
By the end of the first obstetric month (28 days), the fetus has a spine, muscular system and limbs. Points are visible on the head - eyes, nose and mouth. The heart works actively and pumps blood through the forming vessels. On the 27th day, the creation of the neural tube is completed.
When observing the development of the embryo by week, I would like to note the importance of the period of laying the internal organs. The buds received from 14 to 28 days begin to develop actively. At 5 weeks, the liver, pancreas, lungs, larynx and trachea are formed. Sections of the brain and germ cells are laid, the sense organs develop, the circulatory system grows.
The limbs, the upper lip and the nose are distinguishable, the rudiments of the nails and the umbilical cord appear. For 6 weeks, the formation of the brain, facial muscles, upper limbs and internal organs continues. During these 7 days, the length of the embryo will increase from 1.5 mm to 5 mm. Fingers appear on the handles, and eyelids appear on the eyes.
By the end of 8 weeks, the size of the fetus in the egg will increase by another 16 mm. In 14 days, the embryo will finally switch to feeding through the umbilical cord. His face will acquire human features, he will learn to open his mouth. The bones will begin to harden, the membranes between the fingers will disappear. At this stage, the embryo is no longer called the embryo, from that time it is the fetus. The periods of development also change, from embryonic to fetal.
Fetal period
With the end of 2 months, the critical periods of embryo development become less. From 9 to 20 weeks, the baby begins to grow and develop intensively, he gains weight by leaps and bounds. Starting with a pea, the fruit will pick up up to 350 g.
After 56 days, the fetal heart begins to work at a frequency of 150 beats per minute, pumping blood through the vessels, the endocrine system develops, and cartilage tissues are improved. Over the next 7 days, the sucking reflex will be laid, the tail at the bottom of the spine will disappear, buttocks will begin to form.
The embryo moves freely in the egg. His movements are not entirely chaotic, he can consciously move his head and limbs, push off from the walls of the uterus. At 11 weeks, the iris of the eyes will form, which will determine their color. By the end of the 3rd obstetric month, the fetus has eyebrows and cilia, the genitals develop, and the neck is visible.
From 84 to 112 days of embryo development, the nervous and digestive systems are improved in the egg. The pancreas and thyroid glands begin to work, producing hormones. The urinary system "turns on", the bones are already stronger, the skin is thin and wrinkled, red in color, covered with fluff.
The face and limbs are shaped. The baby, being in the egg and swimming in the amniotic fluid, can make faces, frown and smile. Ultrasound shows the sex of the child.
Starting from the 17th week, you can feel movements, the heart is listened to with a stethoscope. The head of the fetus is raised, the fists are clenched. Until the end of the 5th month, he will learn to suck his finger, blink, hear sounds from the outside and react to them. The endocrine and circulatory systems are actively working, the composition of the blood changes. In the egg, the fetus is asleep and awake. By the end of 20 weeks, its weight is about 340 g, height - up to 25 cm.
At the 6th month of the baby's development in the egg, he actively moves. Until 154 days, the formation of the spine and joints will end. By the end of the month, an emotional connection with the mother will be established. The respiratory rate increases up to 55 times per minute, and the genitals are actively developing.
From 25 to 28 weeks, the formation of internal organs ends. Babies born at 7 months are already able to survive. During this period, their lungs and bone marrow are actively developing, the endocrine system and cerebral hemispheres are working. The sense of smell appears, an individual metabolism is created. The weight of the fetus is already about 950 g, the height is 38 cm.
For the 8th month, the baby gains weight, increasing it 2 times. The subcutaneous layer accumulates, the folds are smoothed out, the body becomes lighter. During periods of sleep, the eyes are closed. In bright light of the abdomen, the child squints, his pupils narrow. The work of internal organs is improving, the kidneys produce up to 500 ml of urine, the number of convolutions in the brain increases, the lungs are formed.
From 33 to 36 weeks, the embryo is actively preparing for an independent life. The nail plates are completely formed, the skin brightens and has a good fat layer. By the end of the 9th obstetric month, the weight of the fetus in the egg can be from 2 to 3 kg, the height is about 48 cm. The skeleton has become stronger, only the bones of the skull remain soft. The fruit unfolds with its head down.
During the 10th month, the digestive system improves, the lungs, nose and ears become more elastic. 2 weeks before giving birth, the baby begins to press his head against the pelvic bones, preparing his way.
He is fully formed, the body is in proportion. During this period of development, the embryo gains weight by day, equal to 35 g per day. Birth weight can range from 2 to 4 kg. The normal term for childbirth is considered to be the period from 38 to 40 weeks.
Critical periods
The first 2 months after conception are considered the most dangerous. For 1-2 weeks, there is a high probability of abnormal development of the ovum. It may not descend into the uterus or not gain a foothold in it. As a result: miscarriage or ectopic pregnancy.
The onset of pregnancy is the beginning of an amazing time for the expectant mother. Seeing two cherished stripes on the test, I can't wait to find out what awaits next on the upcoming path of bearing crumbs. Today we will tell you how the fetus develops by weeks of pregnancy, what the mother feels at the same time, and at what stages all organs and systems of the baby's body are formed.
Starting point: how to know when the pregnancy started
The obstetrician calculates the date of the beginning of the expectation of the baby for the woman during the first visit to the antenatal clinic.
- The doctor performs a manual examination to determine the size of the uterus. This will help him understand what period of pregnancy the uterus corresponds to.
- Also, the local doctor must specify the date of the first day of the last menstruation. This moment is taken into account, because the mucous membrane of the uterus begins to prepare for pregnancy from this particular period of time.
- You can find out the most reliable information about the duration of pregnancy using an ultrasound scan. An ultrasound study can tell up to the day when a small life was born. An examination even at the earliest stages (starting from 4-5 weeks) estimates the size of the embryo, which allows the obstetrician-gynecologist to calculate the exact date of the onset of pregnancy.
In the first week after conception, the embryo actively moves along the fallopian tube. After six days of active “travel”, it enters the uterine cavity. Under the influence of progesterone (it is also called the pregnancy hormone), the future baby is attached to the mucous membrane of the uterus, this process is called implantation.
If the embryo is successfully attached, then the next menstruation will not happen - the pregnancy has begun.
Intrauterine development of the child
The development of an infant inside the mother's womb, from the moment of conception to the moment of birth, is usually called a miracle, and there is every reason for this. Fortunately, medicine has studied quite well all the stages of the most important event in a woman's life - pregnancy. Each expectant mother can imagine exactly what will happen to her and her baby during all nine months.
There are three periods of intrauterine development of a baby:
- blastogenesis- starts with fertilization and lasts 15 days;
- embryonic period- starts from the 16th day and ends by the 13th week of pregnancy;
- fetal period- from 13 weeks and lasts until the very birth.
Each of the periods has its own chronology of events. The formation of the child's organs, systems of vital activity in his body and his direct growth naturally move in each period of intrauterine development. How this happens, to find out what and when is formed, you can find out in the summary table. It will be informative for expectant mothers who are interested and important in information about the development of the child at all stages of the pregnancy.
Pregnancy development by week
Waiting for the birth of a baby in obstetrics is usually divided into three conditional parts:
- I trimester - from the beginning of pregnancy until the 13th week;
- II trimester - from the 14th to the 26th week;
- III trimester - from the 27th to the 40th week.
These trimesters contain 10 obstetric months. Conditional split table:
| Obstetric month | Weekly pregnancy period |
|---|---|
| First month | From the first to the fourth week of pregnancy (1-4) |
| Second month | From the fifth to the eighth week (5-8) |
| Third month | Week 9 to 12 (9-12) |
| Fourth month | Thirteenth to Sixteenth (13-16) |
| Fifth month | Seventeenth to Twentieth (17-20) |
| Sixth obstetric month | Twenty-first to twenty-fourth (21-24) |
| Seventh month | Twenty-fifth to twenty-eighth (25-28) |
| Eighth month | Twenty-ninth to Thirty-second (29-32) |
| Ninth month | Thirty-third to thirty-six (33-36) |
| Tenth month | Thirty-seventh to fortieth (37-40) |
Before a detailed study of the process of fetal development in the mother's abdomen, it is necessary to familiarize yourself with the table of changes in the height and weight of the future fetus:
| Week of pregnancy | Fruit size | Fruit weight |
|---|---|---|
| 1 | – | – |
| 2 | – | – |
| 3 | 0.15-0.2mm | – |
| 4 | 1 mm | – |
| 5 | 1.25-1.5mm | – |
| 6 | 2-4 mm | – |
| 7 | 4-5 mm | – |
| 8 | 1.6-2 cm. | 1 g |
| 9 | 2.3 cm. | 3-4 g. |
| 10 | 3-3.1 cm. | 5 g |
| 11 | 4.1 cm. | 7 g |
| 12 | 5.4-6.3 cm. | 13-14 g. |
| 13 | 7.4-8 cm. | 20-23 g. |
| 14 | 8.7 cm. | 35-43 g. |
| 15 | 10-11 cm. | 50-60 g. |
| 16 | 11.6 cm. | 80-90 g. |
| 17 | 12-13 cm. | 100-110 g. |
| 18 | 14.2 cm. | 150 g |
| 19 | 15.3 cm. | 200-210 g. |
| 20 | 16.4 cm. | 260-270 g. |
| 21 | 19-20 cm. | 300-310 g. |
| 22 | 21-22 cm. | 350 BC |
| 23 | 23 cm. | 450 BC |
| 24 | 24 cm. | 550 BC |
| 25 | 25-26 cm. | 680-700 g. |
| 26 | 33 cm. | 800 BC |
| 27 | 34 cm. | 950 BC |
| 28 | 36 cm. | 1-1.3 kg. |
| 29 | 37 cm. | 1.4 kg. |
| 30 | 38 cm. | 1.5 kg. |
| 31 | 39 cm. | 1.6 kg. |
| 32 | 42 cm. | 1.7 kg. |
| 33 | 43 cm. | 1.9-2 kg. |
| 34 | 44 cm. | 2.2 kg. |
| 35 | 45 cm. | 2.4-2.5 kg. |
| 36 | 47.5 cm. | 2.6 kg |
| 37 | 48.5 cm. | 2.9 kg |
| 38 | 50 cm. | 3.1 kg. |
| 39 | 51 cm. | 3.3 kg. |
| 40 | 52 cm. | 3.4 kg. |
Now let's move on to describing the development of the baby in the womb at each week of a woman's pregnancy:
Week 1
The fetus as such is not yet in question, since pregnancy has not actually occurred yet. The main sign that fertilization has occurred is implantation bleeding. This phenomenon manifests itself as a slightly smearing spotting about 6-7 days from the moment of conception.
2 week
This week from the obstetric point of view is considered as possible for conception. The egg cell in the female body matures by the 14th day of the cycle and is theoretically ready for fertilization. If, according to your calculations, the moment of conception has already taken place, then the second week is marked by the attachment of the ovum to the uterus. This moment is important, since from the moment of attachment, the fetus begins its full development.
3 week
The embryo looks like a microscopic berry, in the third week it is still only a set of cells. The size of the embryo is negligible, the maximum diameter by this time is 0.2 mm. But just during this period, the formation of sexual characteristics begins at the cellular level. Having anchored in the uterus, the most important process of intrauterine development of the baby begins - the formation of the placenta. Very little is left before the formation and development of the basic systems of the organism of the unborn child.
4 week
Obstetric 4th week - the period during which the expectant mother discovers two cherished strips on the test. The functional distribution of cells is in full swing in the embryo. Its size can be compared with a poppy seed this week. The weight is still quite insignificant and does not exceed 0.5 g, but the process of cell division occurs every minute and the future baby is growing very quickly.
5 week
The embryo has already passed several stages of its development - zygote, morula and blastocyst. The cells continue to divide rapidly, and by the end of the fifth week the baby will weigh at least 1 g, and the size will reach as much as 1.5 mm. On the ovum, you can already make out the emerging sensory organs - eyes, ears and mouth gap. The blood group of the unborn child was formed just by the 5th week of intrauterine life. The formation of the thyroid gland begins, as well as the intestinal and urinary systems.
6 week
At this time, the unborn child clearly shows the largest parts of the body - the trunk and head. In the form of tiny processes, legs and arms are distinguishable, with tiny fingers protruding on them. The weight at the sixth week in the embryo is up to 2 g, and the average size is about 4 mm. Cartilaginous structures are actively developing, the thymus gland is formed. The main organs continue to develop: the heart, liver, lungs, stomach and pancreas. The baby is developing muscle tissue, the external genital organs are outlined.
7 week
With the beginning of the seventh week, the embryonic period ends. The unborn baby is now called by another medical term - fetus. At this time, the facial features of the crumbs are already slightly distinguishable. The rudiments of the nose, eyelids are formed, the ears and upper lip are visible. Outwardly, “unnecessary” organs are still present - the gills and the tail, which will disappear a little later. The cerebral hemispheres are formed, cartilage tissues develop continuously. The liver at week 7 is already capable of producing blood cells.
8 week
At 8 weeks, the weight of the fetus is 1 g, and the length reaches 20 mm. If you look at an ultrasound scan, then the future baby will look proportionally like a grape. But every day the fruit looks more and more like a real man. The baby's face is already better defined, the nose has small nostrils, and the olfactory recipes are actively formed. His heart becomes four-chambered; ovaries form in future girls, testicles in boys; the arms and legs of the fetus at this time can already bend / unbend.
9 week
Many systems and organs are formed by the 9th week of pregnancy, but they are not yet fully functioning, but continue to develop. The palms are formed, the membranes between tiny fingers disappear. Lymph nodes are laid. The first reflex, the swallowing reflex, begins to develop. The baby's eyelids are formed and can involuntarily open and close. The size of the fruit already resembles a large cherry berry - weight 4 g, height about 30 mm.
10 week
In the 10th week, the baby is actively moving and pushing. But these movements are so weightless that the expectant mother simply does not feel them. The muscles of the face, neck and pharynx begin to develop. The face has already been formed, and in a few weeks the appearance of the unborn child can be examined on an ultrasound scan. The rudiments of milk teeth develop. The cerebellum "acquires" neural connections, which are subsequently responsible for reflexes. A small heart beats at least 150 beats per minute. Now the fruit already weighs 5 g, has grown by about +12 mm and resembles a strawberry.
11 week
The organs and systems of the crumbs have already been formed by this time, some are working in full force, while others continue to ripen. Bronchi, lungs, trachea are actively developing; liver; intestinal tract; blood vessels; irises of the eyes. At 11 weeks on an ultrasound, you can see quite distinguishable outlines of the unborn baby.
12 week
The kid is already actively using some reflexes - imitates breathing and swallowing movements, involuntarily squeezes and unclenches his palms into fists. The first contractions of the intestinal muscles appear (peristatics). The pancreas is formed and is already “learning” to produce bile. A unique pattern appears on the fingertips. The baby develops facial expressions, he can smile or wrinkle his face. Weight - up to 13 g, and height - up to 62 mm.
13 week
A week of an active growth spurt for the future baby. The brain is already capable of giving the first commands for the reflex movements of the fetus. The sense of smell develops, the vocal cords are formed. The body begins to grow faster, and the growth of the head, on the contrary, slows down. In the intestines of the crumbs, digestive villi appear. The baby's skin is still very thin, and is riddled with blood vessels. The weight of the fetus increases up to 20 g, and the growth - up to 80 mm.
14 week
At week 14, all organs and systems of the unborn baby are being improved and continue to grow actively. The ribcage can rise and fall as if breathing - this is how the lungs train. The process of hematopoiesis is formed, sweat glands, neck muscles become stronger every day. The baby's weight at this time is about 27 g, and his height is 110 mm. The lifestyle, nutrition and well-being of the mother are very important - if these indicators are in order, then the baby feels good and does not experience any discomfort.
15 week
This week, the fetus has already formed vision and the necessary nerve endings to be able to see after birth. From the 15th week, skeletal ossification gradually occurs - a long-term process that requires a large amount of calcium. In baby boys, a male hormone, testosterone, begins to be produced. The kidneys excrete the first amniotic fluid. The muscles of the child are improved and strengthened. Fruit weight - 50 g, height - up to 104 mm.
16 week
At 16 weeks, the future baby grows up actively from the top of the head to the very heels. The weight is already about 80 g, and the height can reach 117 mm. The systems of the body function to the best of their ability, some of them already “work” quite well. When the amniotic fluid is swallowed, it travels through the digestive tract and kidneys and becomes urine. The skeleton stiffens, the child's legs are lengthened. The baby is actively moving in the uterus.
17 week
The auditory formation of the unborn baby by the 17th week smoothly ends. The weight is approaching the 100 g mark, and the growth becomes about 12 cm. The blood vessel system develops and branches out. In the baby's blood, the most important components of their own immunity appear - interferon and immunoglobulin. In female children, the uterus is formed in utero. The strength of the baby's pushes increases during this period, they become frequent and tangible.
18 week
The development of the fetus in this period of the second trimester is very intensive. The baby is growing so fast that it could already fit in the palm of your hand. The movements are palpable, the baby moves very actively at 18 weeks. Often swallows amniotic fluid, which can lead to hiccups - this moment the expectant mother can notice by a slight tremor of the abdomen. Gradually, a layer of subcutaneous fat forms in the fetus, muscles develop, and the mineralization of the skeleton continues. Weight - about 150 g, height does not exceed 14 cm.
19 week
The child inside the uterus is actively growing, improving and gaining weight. By the way, the baby weighs about 200 g by week 19, and his height is about 14-15 cm. The body focuses on the development of the brain, the improvement of the five basic senses. The amount of subcutaneous fat increases. The respiratory system continues to develop and strengthen. The period of wakefulness alternates with a period of activity, the baby can sleep up to 16-18 hours a day.
20 week
Outwardly, your baby has already become a real little man, and on an ultrasound scan you can already see the sex of the child, his facial features, observe facial expressions (which sometimes shows the character traits of the future child). The weight of the baby at the “equator” of pregnancy is about 250-270 g, and the average height is 16 cm. The child is active, turns his head, sucks his fingers, opens and closes his mouth.
21 week
At this time, you can already be sure that the child distinguishes sounds and hears what is happening outside the uterus. In terms of body proportions, the baby already practically resembles a newborn. The weight of the fetus is about 300 g, the height is 19 cm. At this time, taste buds are actively formed, and the composition of the blood is improving.
22 week
The twenty-second week is the period when the unborn child prefers to spend most of the time sleeping. But, nevertheless, in a dream, the baby is actively turning over, the size of the uterus still allows you to change the position. The crumb is spinning, pushing, pulling the umbilical cord. The weight at this stage is about 350 g, and the height is 20-21 cm.
23 week
The next week meets with habitual movements, although many babies prefer to “calm down” by 23-24 weeks and make their mothers worry about rare movements. The crumbs still have enough room in the uterus, so many of its tremors are simply not felt, so there is no need to worry. The weight is already moving towards the 450 g mark, and the height is more than 22 cm, although it is worth remembering: all the listed parameters are individual.
24 week
Under the mother's heart, the future baby grows and gains weight - the indicator for many future children at this time is at least 550 g. This week, the development of the infant's bronchi ends, which is very important for the child's respiratory system as a whole.
25 week
From the 25th week, the child in the womb begins to produce pigment in the hair, giving them the color that is due to heredity. It is this color that the mother will see in the baby at his birth. Weight reaches 700 g, height - 23-25 cm. Nerve connections and brain cells continue to form. Training breathing movements can be observed in the fetus.
26 week
Tremors at twenty-six weeks become strong, distinct, and many moms may even complain of their intensity. The child's weight is already at least 800-850 g, and his height is already more than 33 cm. The active strengthening of the bones of the skeleton continues, the rudiments of milk teeth in the gums are mineralized. Marigolds and hairs begin to grow.
27 week
The growth of the child at this time is about 34 cm, and the weight is close to 1 kg. The baby becomes cramped in the uterus, and the legs cannot be extended, so the baby takes an optimal position: pulls small crossed legs and arms to the chest. From the twenty-seventh week, the child is already gradually taking the correct position in the uterus, but if he lies across or "sits on the bottom", then there is still time to roll over.
28 week
With the beginning of the 28th week of pregnancy, the weight of the fetus is up to 1300 grams, and the growth is up to 37 cm. The child's muscle tissue continues to develop intensively. New convolutions are formed in the cerebral cortex. Rh-conflict between the mother and the fetus is possible, and at this time the obstetrician-gynecologist must take special measures.
Week 29
The weight of the fetus is about 1500 kg, and the body length is at least 38 cm. It is time for the expectant mother to master the method of calculating movements.
30 week
The full growth of the fetus reaches 36-38 cm, the weight reaches 1.5 kg. The expectant mother may have several fears that are associated with future childbirth.
31 weeks
At the 31st week of pregnancy, the weight of the fetus will be about 1.6 kg, the full height is about 39 cm. The baby develops pain sensitivity. Possible disturbances in the night sleep of a pregnant woman due to active and strong tremors of the fetus. Now is the time to study the issues of pain relief during childbirth.
32 week
The weight of the fetus is about 1.7 kg, the size from the crown to the heels is 40-42 cm. Abrupt movements can cause dizziness and nausea in a pregnant woman. It's time to think about the possible presence of someone close to you at birth.
33 week
The weight of the fetus by 33 weeks is about 2000 g, the height is 42-43 cm. The mineralization of the bones of the fetus is almost complete. The expectant mother should count the fetal movements from time to time.
34 week
The growth of the fetus is on average 43-44 cm, weight 2.2 kg. The baby becomes very cramped in the uterus, and motor activity decreases. It is time for the mother to discuss with the doctor the method of delivery: a natural birth or a cesarean section.
35 week
The growth of the fetus is 45-46 cm, weight is 2300-2500 grams. The fetus is almost completely ready for childbirth, but the lungs are not yet ready to perform the respiratory function. It's time to pack up for the hospital. If the baby in the uterus has not yet taken the correct position, special exercises will help.
Week 36
Fruit weight is approximately 2.5-2.7 kg. Full growth is about 45-47 cm. At this time, the indicators of each crumb can differ greatly from the average in a smaller or larger direction. It's time for parents to make a to-do list to plan and complete before the baby is born.
37 week
The thirty-seventh obstetric week of pregnancy is the time when the mother must be mentally prepared for the birth of the child. This is especially true of multiple pregnancies and childbirth, starting with the second child. The weight of the child reaches 2.9 kg, and the height is within 50 cm.
38 week
Thirty-eighth week can be the last week of your pregnancy. The child gradually becomes heavier. The baby weighs about 3 kg, and is already 48-50 centimeters tall. Childbirth can begin at any time, so loved ones should be within reach at all times.
39 week
At the 39th week, the mother is not only physically, but already mentally prepared for childbirth. The baby weighs about 3 kg, and its height is about 48-50 cm. The size of the child at this time is similar to a miniature watermelon.
40 week
At the end of this week, the estimated date of the baby's birth may come. The baby's weight is already about 3.5 kg, the height is about 51-55 cm. The baby is completely ready for birth. It remains to wait for the moment when he will make the newly-made parents happy with his birth.
Total.
This is how 40 weeks of pregnancy go by. A happy start to a new life - watch the video of how the crumb develops in the mother's belly:
Development of pregnancy by months: how the mother's body changes and the baby grows
1st month
Mama. The chest becomes sensitive, touching it - painful. The uterus begins to grow gradually.
Child. So far, the future baby is called an embryo. During the first six days of pregnancy, he swims in amniotic fluid, lives "autonomously" and is not yet connected with his mother. Outwardly, the embryo resembles a tiny auricle 5 mm in size. By day 21, his heart begins to work; in parallel at the same time, important organs are formed: the spinal cord and the brain. By the end of the 1st month, the umbilical cord appears, connecting the baby with the future placenta.
2nd month
Mama. Pregnancy is not yet outwardly noticeable either to the expectant mother or to others - the uterus is in a small pelvis, and its size is small. Changes continue to occur in the breast, it swells and increases in size.
Child. This month, changes are coming in the appearance of the unborn baby - facial features appear, the outlines of the eye sockets appear; there is the formation of tiny arms, legs and even fingers on them. The weight of the embryo at this time is up to 8 g, and the size is about 4 cm.
3rd month
Mama. Intensive growth occurs in the uterus, it develops, in size it already fills the small pelvis and almost reaches the bosom. Very soon everyone will see that you are in a position!
Child. By medical standards, your baby has already passed the embryonic stage and is now becoming a fetus. Its weight can reach 65 g, and its length varies from 10 to 12 cm. An important point in development - in the 2nd month, the child has an inner and an outer ear. The baby is very active, moves its arms and legs, nods its head and clenches its fists. The growing child already has eyelids, and thanks to them, he can open and close his eyes.
4th month
Mama. A rounded tummy is already looming, the waist begins to gradually "blur". The mammary glands cause considerable discomfort due to their growth and sensitivity - you have to choose a suitable sleeping position for a long time.
Child. Your baby already has quite a tangible weight - up to 250 g. Most of the time the child spends swimming in the amniotic fluid, their renewal occurs every 3-4 hours. A fluff appears on the baby's head, eyebrows and eyelashes on the face. In the intrauterine development process, the first feelings and sensations begin to form in the child. The baby reacts to loud sounds and a bright light source.
5th month
Mama. Almost every day, the belly of the expectant mother becomes larger and clearly protrudes forward. The uterus is located about 8 cm below the navel. Starting from 17 weeks, most expectant mothers begin to feel new sensations in the stomach - while weak, but very pleasant pushes and movements of their baby.
Child. In the fifth month, the child's brain is actively growing, the nervous system develops. The heart beats twice as often as that of the mother. By this period, the weight of the crumbs can be up to 650 g, and the height is about 30 cm. By the 20th week, the baby is already able to suck his fingers on his hands, and at 24 weeks, he can open his eyes and react to light.
6th month
Mama. The waist of a pregnant woman by this time becomes 8-10 cm larger. The size of the uterus increases so much that now it reaches the navel. The state of health and mood is good, the weight has not grown too much and the activity of the expectant mother is not limited by anything.
Child. It's time for the baby's respiratory system to mature. The lungs begin to mature after 24-25 weeks of gestation. The child has already formed sensations of light and noise - when he hears a sharp sound, the baby can shudder. The first reflexes (hiccups, swallowing and sucking reflexes) also appear and actively develop.
7th month
Mama. The size of the uterus by the seventh month of pregnancy reaches 24-28 cm in height, it continues to grow and grows with the baby.
Child. The baby is already less active than in earlier periods. In most cases, the baby settles down in the uterus, head down, and sleeps for a long time. The child's weight is already 1-1.2 kg, and his height is up to 37 cm. He is already learning to breathe, but the lungs are not yet mature enough - they will finally be ready for the breathing process at about 34 weeks, which is important in case of premature birth. By this time, the baby has already learned to recognize the mother's voice, and recognizes it when he hears it.
8th month
Mama. The body of the expectant mother continues to change - the uterus rises up already by 30 cm, contracting from time to time, as if “rehearsing” the upcoming contractions. Colostrum appears in the breast. In the third trimester, the load on the female body increases many times over, and existing chronic diseases may worsen.
Child. The kid is growing and gaining strength. For the mineralization of bones, the baby needs a large amount of calcium, which comes to him from his mother. The baby's skin becomes pink, smoother. From time to time, a mother can observe protrusions and “bumps” on her belly at those moments when the baby is tossing and turning violently.
9th month
Mama. The body of a pregnant woman begins to actively prepare for childbirth. The uterus, together with the baby, weighs about 6-7 kg at this time, and its height is measured within 33 cm. In the third trimester, pain in the pubic articulation, edema and increased blood pressure are frequent.
Child. After 38 weeks of pregnancy, the development of the intrauterine development of the baby can be considered complete. The baby is ready to be born. In the last month, the baby is gaining 10-15 g daily. Amniotic fluid becomes less and less, the baby grows by leaps and bounds, and it becomes cramped in the uterus. In girls, the labia majora cover the small ones; in boys, the testicles descend into the scrotum. The fluff on the body completely disappears, and only a little primordial grease remains. At the time of birth, the child weighs approximately 3-3.5 kg, and the height varies from 50 to 55 cm.
And finally, photos and recommendations from a young mother. Look at the photo of the growth of the belly during forty weeks of pregnancy. Have you photographed your belly week by week?
During 9 months of embryonic development, the human embryo goes through an amazing path from a cell to a full-fledged, viable organism. Each week of pregnancy is marked by the formation of new tissues and organs. If in the early stages a human embryo cannot exist without a mother, then by the end of gestation it becomes more and more independent. How does a child develop in the womb?
The initial period of embryonic development (first 4 weeks)
A new life is born at the moment of fusion of two gametes - a sperm and an egg. If this occurs as a result of natural intercourse, then conception takes place in the fallopian tube, where the sperm wait for the egg to leave the follicle. In the process of their connection, a new cell appears - a zygote. After 24-36 hours, it begins to split, and on the second day after conception the embryo already consists of 2 cells, on the third - from 8, and on 4 - from 10-20. This form of embryo is called blastocyst.
The blastocyst, due to the contraction of the muscles of the fallopian tube and the movement of the villi, is directed towards the uterine cavity. She enters the uterus on day 7-8. During this time, the hormone progesterone has time to prepare the uterine endometrium for implantation. 
The blastocyst ejects finger-like processes and attaches to the endometrium, hCG begins to be secreted. Some women at this moment feel a pulling pain in the abdomen, they have spotting spotting - implantation bleeding.
If in the first week of pregnancy the size of the embryo is only 0.2 mm, then by the third week it grows to 4 mm. The initial period of embryogenesis is characterized by rapid changes that occur every day. In the third week, the embryo is a gestational egg. It includes directly the human embryo itself and provisional organs that perform the function of not yet formed tissues - chorion, amnion, yolk sac.
A neural tube is formed, which runs along the entire length of the embryo. It has several bulges. By the 21st day of embryonic development, the heart is formed from the middle bulge, from the one on top - the brain. The rest of the tube becomes the spinal cord.
At 4 weeks, the laying of the main organs begins - the liver, kidneys, stomach, intestines. During this period of ontogenesis, the embryo is especially vulnerable, any external influence, illness of the mother, taking medications can affect the embryonic laying of organs. By the end of the first month of gestation, the heart is already beating, blood is circulating, there are rudiments of limbs and eye sockets. In the photo below you can see what a child looks like at this stage of ontogenesis. 
Development stages in the following months
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The intrauterine development of a person is called the prenatal period. It is divided into two parts - the embryonic period (up to 8 weeks) and the fetal period, when the embryo is already called the fetus. All pregnancies are divided into trimesters:
- first trimester - 1-13 weeks;
- second trimester - 14-26 weeks;
- third trimester - 27 weeks and before birth.
The second (from 5 to
At the 5th week of gestation, the umbilical cord is formed in the embryo. She will connect the fetus with the mother's body, it is through her that he will receive useful elements and oxygen and give up waste after metabolism. As the intestine grows, it partially fills the umbilical cord. This is due to its length, which is disproportionate to the size of the embryo. At week 10, it will be completely hidden inside the body.
By the 6th week, the embryo already has facial features, it has eyes that are covered with eyelids, a nose, and jaws.
The limbs continue to form, but the baby can already bend his arms at the elbows, clench his fists. In the middle of the second month of gestation, the weight is 2 g, and the body length is 2.3 cm.
At the 7th week of the embryonic period, the placenta begins to form, which immediately takes over the function of secreting hormones. Internal organs develop - blood vessels, endocrine glands, brain, sex glands - testes or ovaries.
At the 8th week of gestation, the Y-chromosome site, which is responsible for the production of sex hormones, is activated. If a woman is pregnant with a boy, the testes secrete the hormone testosterone. Under the influence of this hormone, the male genitals will form in the boy. The external genitals are still poorly differentiated, although the genital tubercle, urogenital and anal membranes have already been formed.
Third (9 to 12)
In the third month of pregnancy, the embryonic period of ontogenesis ends and the fetal period begins. By week 10, many structures have already been formed:
- oral cavity;
- face;
- large hemispheres;
- intestines;
- bile ducts.
The cerebellum begins to develop. The fetus makes the first movements in the womb, but it is still too small for the woman to feel them.
The initially uniform genital tubercle, under the influence of sex hormones, begins to differentiate by week 12. In a girl, this leads to the formation of a clitoris, large and small labia, and in a boy - a penis and scrotum.
At 12 weeks gestation, you can already tell what blood type the child will have. Agglutinogens appear on the surface of erythrocytes, which determine the group affiliation and the Rh factor. T-lymphocytes appear in the thymus, which play an important role in the body's immune response.
Fourth (13 to 16)
The table provides a weekly description of the growth and weight of the embryo at 4-5 months of the embryonic stage:
The child has formed many organs that have already begun to function in accordance with their role in the body:
- the pancreas produces the hormone insulin;
- the liver secretes bile;
- the heart muscle distills 600 ml of blood;
- the kidneys excrete urine;
- the thyroid gland secretes thyroid hormones;
- the bone marrow produces blood cells (erythrocytes, leukocytes);
- sweat and salivary glands begin to function;
- the genitals are fully developed, but it is still not easy to see them on ultrasound;
- boys develop a prostate gland;
- oogonia breed in girls - by the time of birth, only 3-4% of the original number will remain.
At the beginning of 13 weeks, the placenta is already fully formed. It provides the baby with the necessary nutrients for development, and also produces progesterone and estrogen necessary to maintain pregnancy.
Outwardly, the fruit looks like a little man. Eyes and ears take their usual place, eyebrows and hair on the head grow. The whole body of the baby is covered with fluffy hairs - lanugo. The rudiments of milk teeth are laid in the mouth. The skeleton, muscles, ligaments are actively formed. The fetus carries out many movements of the limbs, fingers, head.
Fifth (17 to 20)
In the fifth month, the following organs and structures are gradually formed:
- the development of the immune system ends;
- the auditory system is formed - the ear bones and the brain area responsible for hearing; the child can hear sounds;
- a uterus appears in girls, follicles grow in the ovaries;
- milk teeth are covered with dentin, rudiments of a permanent dental kit are formed under them;
- myelination of the nerves begins.
Many organs have already been formed, and from this moment their improvement begins. The brain already contains zones responsible for smell, touch, taste, sight and hearing. On ultrasound, you can see the sex of the unborn baby.
The fruit can tell the time of day. He actively moves in the womb, feels the space around - his own face, the wall of the fetal bladder, the umbilical cord, puts his fingers in his mouth, and uses more with one hand. He prefers to sleep most of the time.
The body of the fetus is covered with a cheese-like lubricant - a viscous substance that protects the skin. Under it, the skin is divided into layers. What a child looks like at this stage of ontogenesis can be seen in the photo.
Sixth (21 to 24)
A period of active growth of the child begins. If at 21 weeks he weighs 360 g, then at 24 he is already 500-600 g. His body supports the spine, which has 33 vertebrae and 150 joints. The baby continues to move in the mother's belly, his inner ear has formed, and he knows what position he is in. An individual pattern appears on the fingers, which will remain so for life.
The amniotic fluid becomes the food source. The fruit drinks it, and he can already taste it thanks to the taste buds on the tongue. In the large intestine, carbohydrates are absorbed from the amniotic fluid. Waste is excreted in the urine.
The bone marrow takes over the production of red blood cells. Until the sixth month, the liver and spleen were engaged in this.
The alveoli inside are covered with a suffractant. This substance prevents the lungs from sticking together when breathing. However, there is still too little of it, therefore, when the child is born during this period, the child is nursed in an incubator.
Internal genitals and external genitals continue to develop. Girls have a vagina, and boys' testicles begin to descend from the abdominal cavity into the scrotum.
Seventh (25 to 28)
In the seventh month, the third trimester of pregnancy begins. The child continues to grow rapidly. At 25 weeks, it weighs 710-760 g, and at 27 it reaches 1 kg and 35 cm.
The already formed organs continue to improve. The eyes are still closed, but they have formed an iris - blue or dark. Eyelashes, eyebrows, hair on the head grow, and the hair on the body, on the contrary, begins to disappear.
Mothers note that the baby often moves in the stomach, changes position. A woman can already determine when her child is asleep, and when he begins a period of activity. In a dream, the fetus can suck a finger, smile.
The brain is improving. The pituitary gland produces adenocorticotropic hormone, which stimulates adrenal development and glucocorticoid secretion.
Eighth (29 to 32)
At the eighth month, the growth of the fetus occurs according to an individual scheme. This is influenced by many factors, including genetic ones. Some babies are born large, while others are miniature. On average, at 29 weeks, the weight of the fetus is 1150 g, and the growth is 36 cm, at 32 weeks - the weight is 1400-1900 g.
The child has all the organs formed, if the mother begins premature birth, the baby will survive. However, there is still little suffractant, so medical attention and nursing will be required.
At this stage of gestation, it is important to find out what position the fetus is in. It can be located longitudinally, transversely or obliquely. To select a management strategy for labor, it is important to determine the presentation, which can be cephalic or pelvic. The most successful is the head position, but if the child is lying with his buttocks down, you should not worry, he has several weeks to turn around. The doctor monitors the location of the fetus on an ultrasound scan.
Ninth (33 to 36)
At 33-34 weeks, the growth and weight of the baby is 40 cm and 1800-2100 g, and by the end of 9 months - 46 cm and 2400 g. If the fetus is born right now, it can survive even without the help of medical personnel. All of its organs are formed and functioning. Below is a photo of the fetus just before birth.
The nervous and immune systems continue to form, the subcutaneous fat necessary for thermoregulation is built up. The bones of the baby's skull are mobile, he will need this when he goes through the cervix and vagina - the bones will move over each other. The child is already quite large, there is little room for him in the uterus, so he practically does not move.
Last weeks before childbirth (37 to 40)
In the last weeks before giving birth, the baby is fully formed and awaits birth. During the waiting period, he gains weight, which at the time of delivery is on average 3000-3500 g.
All organs have already taken shape and are functioning normally. The grease disappears, which is why some babies are born with wrinkled skin.
Not all women give birth at exactly 40 weeks. Delivery can occur with a delay or an advance of 1 week, this is normal and depends on the individual characteristics of the course of gestation.
When passing through the birth canal, the baby's head is deformed, he is born covered with mucus and blood. Obstetricians who deliver childbirth free the mouth and nose from mucus, the baby takes the first breath and makes the first cry - he notifies everyone that he was born.
