How much the embryonic period differs from the obstetric one. What is the difference between obstetric weeks and ordinary weeks
The duration of a woman's special condition is measured in obstetric months and weeks. The obstetric week lasts the same as the usual one. A month is 4 weeks long.
Obstetric weeks of pregnancy will help determine the expected date of birth
The obstetric gestation period is 14 days longer than the real one. Pregnant women are worried about many questions, one of them is why such a difference is obtained.
Why consider obstetric weeks of pregnancy?
It is a mistake to believe that pregnancy occurs at the moment of fertilization of the egg by the sperm. In fact, pregnancy can be ascertained after the fertilized egg is implanted in the uterus. This does not always happen. For various reasons, the body may reject the embryo, then pregnancy does not occur, despite fertilization.
This process usually occurs either at the time of ovulation or during the next day. Therefore, the embryonic maturity of the fetus can be considered from the moment of ovulation. However, this method is not suitable for further monitoring of pregnancy, as the date of ovulation may shift. Even in completely healthy girls, ovulation can begin a little earlier or later than the due date. Because of this, it is impossible to accurately calculate the embryonic age of the fetus.
Ultrasound will not help determine how many days the fetus
The obstetric period began to be calculated in ancient times, when little was known about the characteristics of the female body, including doctors of those years who did not know about ovulation. The main symptom of pregnancy then was the absence of menstruation. Therefore, to consider the period of development of pregnancy began from the date of the last menstruation. This method is quite accurate, so modern gynecologists also take into account the obstetric period. It is on him that they lead the pregnancy.
If you want to conceive a child, you can make it easier for doctors. Use ovulation tests or determine this period of your cycle using improvised methods, such as taking a temperature. So you will know exactly the date of conception of the child and will be able to determine the date of birth as close to reality as possible.
How to calculate obstetric term?
It is generally accepted that pregnancy lasts 9 months. But here the question arises: which months to count, because one has 28 days, the other 30, and the third can even be 31. Here the calculation of the obstetric term comes to the rescue, according to which the pregnancy lasts exactly 40 weeks.
To calculate the estimated due date, you can proceed in two ways:
- From the end of the last menstruation before pregnancy, count 280 days.
- From the beginning of the last menstruation, count 9 months and 7 days.
In any of these ways, you will receive an estimated date for your visit to the hospital. However, remember that the date is not just called hypothetical. Rarely women give birth right on time. Normally, childbirth occurs from the 38th to the 42nd week. A baby born before the 38th week will be considered premature, and after the 42nd week - post-term. Between the 38th and 42nd week, the baby may be born immature, but he will always be considered full-term.
Is it possible to determine the period with the help of ultrasound?
The hope that an ultrasound will determine the duration of your pregnancy is not justified. This study can assess the degree of development of the child according to his obstetric age. Therefore, the period must be estimated even before going to the office of an uzist.
Now you know how important the obstetric period is. During pregnancy, each stage plays a role, so approach this issue responsibly.
Maria Sokolova
Reading time: 8 minutes
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The obstetric method of calculating pregnancy by week is different from the usual one. A month consists of 28 days, not 30-31. As a rule, the gynecologist considers the period from the first day of the last menstruation. The waiting period for a baby is only 40 obstetric weeks.
Consider how the fetus develops weekly, and also determine what mommy feels at all stages of pregnancy.
1 obstetric week
The fetus is a follicle that appears on the surface of the ovary. Inside it is an egg. The female body does not feel it, but only prepares for fertilization.
There are no symptoms of conception at 1 week of pregnancy. And all because the fetus does not manifest itself. The expectant mother will not even notice the changes.
2 obstetric week
At this stage of development, ovulation occurs. As soon as the egg matures in the follicle, it is released from it and goes through the fallopian tube to the uterus itself. It is during this period that the sperm gets to it and merges together. This forms a small cell called a zygote. She already carries the genetic material of both parents, but does not manifest herself.
The body of the expectant mother may behave differently at 2 weeks after conception: signs of PMS may appear, mood will change, you will want to eat more or, on the contrary, will turn back on food.
3 obstetric week
On the 14-21st day of the menstrual cycle, the fertilized cell joins the uterine layer of the endometrium and is placed in a special water bag. The embryo in this period is very small - 0.1-0.2 mm. He has a placenta.
In a pregnant woman at 3 weeks, the hormonal background changes. Symptoms of PMS can be noticeably expressed: the chest will begin to swell and ache, the lower abdomen will be pulled, the mood will change. In addition, early toxicosis may occur.
But in many women, such signs were not observed at this stage of pregnancy.
4 obstetric week
At the 4th week of conception, the fetus establishes a connection with its mother - an umbilical cord is formed, through which the baby will eat all 9 months. The embryo itself consists of 3 layers: ectoderm, mesoderm and endoderm. The first, inner layer is responsible for the creation in the future of such organs as: the liver, bladder, lungs, pancreas. The second, middle word is needed to create the muscular system, the heart, kidneys, circulatory system and gonads. The third, external, is responsible for the skin, hair, nails, teeth, eyes, ears.
In the mother's body, malaise, drowsiness, irritability, nausea, soreness of the mammary glands, improved appetite, and fever may occur.
5 obstetric week
At this stage, the embryo has some inclinations of the nervous and respiratory systems, and the heart and blood vessels are fully developed. The fetus weighs only 1 gram, and its size is 1.5 mm. At 5 weeks after conception, the baby's heart begins to beat!
Symptoms in a pregnant woman are as follows: morning sickness, chest enlargement and pain, fatigue, drowsiness, increased appetite, sensitivity to odors, dizziness.
6 obstetric week
Your baby's brain is forming, arms and legs, eye pits appear, and folds appear in place of the nose and ears. Muscle tissue also develops, the embryo begins to feel and manifest itself. In addition, he formed the beginnings of the lungs, bone marrow, spleen, cartilage, intestines, stomach. At 6 weeks from conception, the fetus is the size of a pea.
Despite the fact that a third of pregnant women do not notice changes in the body, women may experience fatigue, frequent urination, toxicosis, abdominal pain, mood changes, and breast enlargement.
7 obstetric week
At this time, the child develops very quickly. It weighs 3 g, and its size is 2 cm. Five sections of the brain are formed in it, the nervous system and organs (kidneys, lungs, bronchi, trachea, liver) develop, optic nerves and the retina of the eyes are created, an ear appears, nostrils. Slowly, the baby has a skeleton, the rudiments of teeth. By the way, the fetus has already developed a four-chambered heart and both atria work.
In the second month of pregnancy, everything also changes mood. A woman notices rapid fatigue, she wants to sleep constantly. In addition, performance may decrease, toxicosis may appear, heartburn and bloating may torment. Many pregnant women experience low blood pressure during this period.
8 obstetric week
The baby already looks like a person. Its weight and size does not change. He is like a grape. On ultrasound, you can already see the limbs and head. The baby actively manifests itself, rolls over, squeezes and unclenches the hands, but the mother does not feel it. At 8 weeks after conception, the fetus has already formed all the organs, the nervous system is developed, the rudiments of male and female genital organs appear.
A pregnant woman in the second month may feel discomfort in the lower abdomen, as the uterus will increase and will be the size of an orange. In addition, toxicosis manifests itself, appetite changes, mood changes, working capacity decreases, and frequent urination appears.
9 obstetric week
At the beginning of the third month of pregnancy, the cerebellar region is formed in the fetus, which is responsible for the coordination of movements. In a child, the muscle layer increases, the limbs thicken, palms are created, genitals appear, the kidneys and liver begin to work actively, the back straightens and the tail disappears.
The expectant mother feels discomfort, also quickly gets tired, suffers from toxicosis, does not get enough sleep, but feels better than last week. The chest in this period increases dramatically.
10 obstetric week
The size of the fetus is almost 3-3.5 cm. At the same time, it is actively growing and developing. The baby has chewing muscles, the neck and pharynx are formed, nerve endings, olfactory receptors, taste buds on the tongue are created. Bone tissue also develops, replacing cartilage.
The pregnant woman also suffers from toxicosis and frequent urination. Weight may increase, pain in the groin and chest may occur, and sleep will be disturbed.
11 obstetric week
The embryo of this period is already clearly moving, it reacts to external stimuli (smell, food). He develops a digestive system, genitals. At 11 weeks from conception, rarely anyone determines the sex of the baby. All other organs gain weight and develop further.
A woman can get upset for no reason, want to sleep or refuse to eat. Many can be tormented by toxicosis, constipation and heartburn. There should be no other unpleasant manifestations.
12 obstetric week
At the end of the 3rd month of pregnancy, the internal organs of a small embryo were formed, its weight doubled, human features appeared on the face, nails appeared on the fingers, and the muscular system developed. The child is already wrinkling his lips, opening and closing his mouth, clenching his fists and swallowing the food that enters the body. The human brain is already divided into two hemispheres, boys produce testosterone.
Mom is starting to feel better. The malaise, fatigue pass, the toilet runs less, but the change in mood also remains. There may be constipation.
13 obstetric week
At 4 months, a human develops a brain and bone marrow, a respiratory system, and thin skin appears. The baby feeds through the placenta, this week it has finally formed. The weight of the fetus is 20-30 g, and the size is 10-12 cm.
A woman in the 13th week may suffer from constipation, cramps and changes in blood pressure. She feels better, stays awake. Some people still have morning sickness.
14 obstetric week
This week, the fetus is rapidly gaining weight, its organs and systems are improving. The baby weighs about the same as an apple - 43 g. He has cilia, eyebrows, facial muscles and taste buds develop. The child begins to see and hear.
Mommy now eats with great pleasure, her appetite appears, her breasts and belly increase. But there are also unpleasant sensations - shortness of breath, pulling pains in the lower abdomen. Stretch marks may appear.
15 obstetric week
At this time, it is already possible to determine the sex - the genitals are formed in the fetus. The child develops legs and arms, auricles, the first hairs grow. The baby is gaining weight, his bones are getting stronger.
The expectant mother feels more cheerful, toxicosis and weakness pass. But there may be shortness of breath, impaired stool. Blood pressure will be reduced. Dizziness will remain. Weight will increase by 2.5-3 kg.
16 obstetric week
At the end of 4 months, according to obstetrical calculations, the fetus already weighs like an avocado and fits on your palm. His organs and especially the digestive system begin to work actively. He already reacts to voices, hears and feels, moves. Those mothers who are pregnant with their second child may feel movements in the tummy.
The expectant mother at the 16th week may complain of pain in her legs. Mood and well-being improves. Skin pigmentation may change.
17 obstetric week
At the beginning of the 5th month, the baby becomes more like a newborn, as it forms subcutaneous adipose tissue called brown fat. He is responsible for heat transfer in the body of the child. Also, the fetus gains weight. And he can also eat about 400 g of amniotic fluid. He develops a swallowing reflex.
Mommy can feel the baby move in the tummy, and the doctor will hear his heartbeat. The expectant mother at the 17th week of pregnancy will feel calm, happy and a little distracted. Some women will only be concerned about late toxicosis.
18 obstetric week
The fetus is actively developing, growing, moving, pushing. Fat folds form on the skin. In addition, the child begins not only to hear you, but also to distinguish between day and night. His retina becomes sensitive, and he understands when the outside of the tummy is light and when it is dark. All organs, except for the lungs, function and fall into place.
Mommy's weight at week 18 should already increase by 4.5-5.5 kg. Appetite will increase, as the baby will have to feed. A pregnant woman may feel discomfort in the abdomen, vision may deteriorate. A median line will appear on the tummy.
19 obstetric week
At this time, the nervous system and the fetal brain develop. Respiratory system, lungs improved. His kidneys begin to work actively - to excrete urine. The digestive system is also on the verge of completion. The child actively manifests itself, gives signals and gains weight.
There should be no health problems for the mother. In rare cases, nasal congestion, shortness of breath, constipation, heartburn, changes in blood pressure, convulsions and discharge from the chest will appear.
20 obstetric week
The fetus also continues to develop - the immune system is being formed, the parts of the brain are improving, the rudiments of molars appear. With the determination of sex at this stage of pregnancy, doctors are not mistaken.
Half the term has passed. Feeling good should be great. Some points may be disturbing: vision will deteriorate, shortness of breath will appear, frequent urination, dizziness from low pressure, blood from the nose, swelling.
21 obstetric weeks
At the 6th month of the life, all organs and systems have already been formed in the bladder, but not all of them function as they should. The child already lives according to the sleep-wake regime, swallows amniotic fluid, grows and gains weight. The pituitary gland, adrenal glands, sex glands, and spleen begin to work.
A pregnant woman at 21 weeks should feel good, but she may be bothered by pain in her stomach and back. There may be shortness of breath, heartburn, swelling of the legs, frequent urination, stretch marks, increased sweating.
22 obstetric week
The little man at this time actively begins to tactilely study his mother's stomach. He grabs the umbilical cord with his hands, plays with it, sucks his fingers, can roll over and react to food, light, voice, music. The brain stops developing at week 22, but nerve connections are established.
Mom, as a rule, quickly gets tired, feels unwell. Since the baby is always moving, it is difficult for a woman to find a comfortable position for relaxation. The pregnant woman becomes very sensitive, reacts to smells, food.
23 obstetric week
The child is also actively moving, gaining weight. The digestive system is so well developed that he already eats about 500 g of amniotic fluid. At week 23, the baby can already dream, doctors will record brain activity at your request. The child opens his eyes, looks at the light. He can even breathe - usually takes 55 breaths per minute. But breathing is still unstable. The lungs are developing.
A pregnant woman has contractions at 6 months. They are quite rare and manifest as mild spasms in the uterus. Of course, a woman is gaining weight, and in an uncomfortable position, she may feel pain in her back and stomach. Varicose veins, hemorrhoids may appear. There will be swelling, pigmentation and nausea.
24 obstetric week
In a fetus of this age, the process of development of the respiratory system is completed. The oxygen that enters the baby moves through the blood vessels. A baby born at 24 weeks can survive. The function of the fetus at 6 months is as follows: to gain weight. The future newborn is also in contact with the mother through pushes and movements.
The pregnant woman feels a surge of strength, gains weight sharply. She may be disturbed by swelling of the face, legs, the problem of heavy sweating. And, in general, the state of health is excellent.
25 obstetric week
In the fetus for the 7th month, according to obstetric calculations, the bone-articular system is strengthened, and the bone marrow is finally improved. The baby already weighs 700 g, and its height is 32 cm. The baby's skin acquires a light shade, becomes elastic. Surfactant accumulates in the lungs, which prevents the lungs from collapsing after the first breath.
A woman may suffer from the following troubles: heartburn, constipation, anemia, shortness of breath, swelling, pain in the abdomen or lower back.
26 obstetric week
The peanut is gaining weight, its muscles are developing, and fat is being deposited. The lungs prepare to take in oxygen. The baby's body produces growth hormone. The rudiments of permanent teeth appear.
The skeletal system is getting stronger. The child is already moving so much that it hurts the mother. And mommy suffers from heartburn, shortness of breath, back pain. Anemia, swelling, vision problems may occur.
27 obstetric week
The bubbler actively trains all organs and systems. It weighs about 1 kg, and its height is 35 cm. The baby also feels extraneous sounds, feels touch, and reacts to light. He has improved swallowing and sucking reflexes. When pushing, the mother may notice the arm or leg of her child.
The health of the mother at the 27th week should be good. She may be disturbed by itching, anemia, convulsions, changes in blood pressure, sweating.
28 obstetric week
At the end of the second trimester, the fetus becomes even more mobile. He has an increase in brain mass, a grasping and sucking reflex is manifested, muscles are formed. The little man lives according to a certain routine - he sleeps for about 20 hours and is awake for the remaining 4 hours. The baby's eye membrane disappears, he learns to blink.
Mom at the end of the 7th month of pregnancy may feel itching, back pain, swelling of the legs, shortness of breath, heartburn. Colostrum comes from the mammary glands. There may be stretch marks on the body.
29 obstetric week
The baby has already grown to 37 cm, its weight is 1250 g. The baby's body can regulate its temperature, its immune system works perfectly. The child gets better, gains weight, accumulating white fat. The baby is almost ready for existence outside the mother's belly, who feels every movement of the little man. In addition, a pregnant woman gets tired of bearing, gets tired quickly, her appetite improves, shortness of breath and bouts of urinary incontinence may appear.
30 obstetric week
At 8 months, the baby is already quite developed. He feels the world around him, listens to his mother's voice. The baby lives according to its own schedule of sleep and wakefulness. His brain grows and develops. The fetus is very active. He can turn from the bright light, push mommy from the inside. Because of this, the woman will feel a slight pain in the abdomen, back, lower back. The load also goes to the legs - they can swell. Also, a pregnant woman may feel shortness of breath, constipation, bloating.
31 obstetric weeks
At this age, the lungs also improve in the crumbs. Nerve cells are active. The brain sends signals to the organs. The liver lobules are completing their formation. The baby also grows and feels the world around him. His mom gets tired faster now. She may be disturbed by shortness of breath, swelling, late toxicosis and pain in the lower back and abdomen.
32 obstetric week
There are no changes in the development of the fetus. He is gaining weight and weighs 1.6 kg, and his height is already 40.5 cm. The child is also sensitive to smells, food, ambient sounds and light. And by the end of the 7th month, he takes a pose for birth. His skin takes on a light pink hue. The expectant mother may complain only of shortness of breath, frequent urination and swelling.
33 obstetric week
At the 8th month of pregnancy, the child performs an important function - gaining weight. Now he weighs 2 kg, and his height is 45 cm. The nervous system develops in the crumbs, new connections are formed. The immune system is also still being formed. The baby becomes less mobile, as it occupies all the space in the mother's uterus. A woman at 33 weeks feels good. She may experience shortness of breath, heartburn, leg cramps, back pain, and itching.
34 obstetric week
The baby is ready to get out. He gains weight and becomes 500 g more. Its organs and systems are trained to function before going out. If the baby is born at 34 weeks, she will already be able to breathe on her own. And the belly button takes calcium from the mother's body and builds further bone tissue.
Mommy may lose her appetite during this period. Will torment back pain, shortness of breath, numbness, swelling. Many women have contractions, but the pain in the upper abdomen should subside.
35 obstetric week
Significant changes in the development of the fetus are not observed. All organs and systems simply debug their work. Final processes take place in the nervous and genitourinary systems. Meconium accumulates in the intestines. From this week, the child is rapidly gaining weight by 200-300 g. And his mother suffers from frequent urination, edema, heartburn, shortness of breath, and insomnia. Contractions are also weak.
36 obstetric week
At the end of the 8th month, the placenta begins to fade. Its thickness is small, but it performs its functions. The child is less active, sleeps more and gains strength before childbirth. Its systems and organs are developed. And the expectant mother may complain of a feeling of fatigue and possible contractions.
37 obstetric week
The baby is ready to be born this week. His vision and hearing have finally matured, his body has formed. The child is already quite like a newborn and is waiting in the wings. Mommy feels discomfort, pain. Contractions may recur more frequently. But breathing and eating will become easier. Your stomach may drop. This phenomenon occurs a few weeks before delivery.
38 obstetric week
The weight of the crumbs is 3.5-4 kg, and the height is 51 cm. The placenta, which connects the baby with the mother, is aging and losing its fullness. The fetus stops growing, as it receives less nutrients and oxygen. The child descends closer to the "exit" and eats through the mother's placenta. He is ready for an independent life.
A pregnant woman feels heaviness in the lower abdomen. Also, she may be disturbed by frequent urination, leg cramps.
39 obstetric week
This week the arrival of the baby will be on time. Girls are usually born before boys. The baby is already viable. Mom is feeling contractions. If they were not observed, in no case should a woman call them on her own. The expectant mother's mood changes, appetite disappears, frequent urination worries.
40 obstetric week
The child is also waiting for the birth, gaining strength. It can grow up to 52 cm and weigh about 4 kg. The bladder does not move much, but still reacts to mom's mood. A pregnant woman, as a rule, is already ready to become a mother. She is worried about irritability, white-yellow discharge, pain throughout the body, nausea, heartburn, diarrhea, constipation, and, of course, contractions.
41-42 obstetric weeks
The child may be born later than the due time. His bones will get stronger, body weight and height will increase. He will feel great, but mom will feel constant discomfort. She may have a stomach ache due to the movements of the baby. There will be constipation or diarrhea, flatulence, insomnia, swelling.
Our online pregnancy calculator will help you calculate your pregnancy by week. Pregnancy is an amazing period in the life of any woman, when a new life appears and develops inside. This is happening at a fairly fast pace. In 9 months, the fetus goes through stages of development from a few small cells to an organized organism. With each week of pregnancy, the little one undergoes certain changes, improves existing systems, acquiring new qualities. Therefore, it is very interesting for the expectant mother to find out during the whole interesting situation what is new with the baby, what he is like, what he can do at this stage. Description next.How to calculate the gestational age by week
For this, an interactive Pregnancy Calculator is intended, which allows you to calculate a woman's pregnancy by weeks, thus finding out the approximate date of birth of the child. The calculation is carried out from the first day of the last menstruation, although it is more correct to consider the term of conception from ovulation. Although the exact time of ovulation is not always known, the pregnancy calculator reflects the timing for the more common cycle of 28 days. With a long or short cycle, amendments are possible, although in practice it is customary to calculate the gestational age of a woman by menstruation. This Pregnancy Calendar is designed to calculate the timing of key moments in fetal development and includes a birth calculator.What is gestational age and how is it calculated? It is customary to single out obstetric and embryonic terms, and many mothers simply get confused in these terms, and today we will try to figure it out.
The first thing we will start with is the obstetric term, because in fact, our gynecologist will make all calculations based on the obstetric term.
obstetric term
The obstetric period is calculated from the first day of the last menstruation, so when you go to the gynecologist for the first time, clearly know the date of your last menstruation, this will make your life easier, and in the future all of your data will be entered in a special card, everything will be written there.
The obstetric period involves 280 days of pregnancy, well, these are averages, it is clear that each mother is an individual and this period may vary, but it is customary to consider 280 days.
According to the obstetric period, they issue directions for tests, a certificate of maternity leave and all other documents that you will need in the future, the same exchange card, where all the data will be put on the basis of the obstetric period.
And according to the obstetric term, the estimated date of birth is calculated, this is the PDR.
How to calculate the expected due date
The first day of the last menstruation, 3 months ago and 7 days are added, so you can calculate your gestational age and when your baby will be born.Embryonic term
It is calculated from the moment of conception and is usually shorter by 14-15 days of the obstetric period.
That is, in fact, we all know biology, menstruation has passed and a new cycle of egg formation has begun, and on day 14-15, on average, it matures and is ready for fertilization, this is called the day of ovulation.
In fact, it will be very difficult for us to determine and calculate the exact day of ovulation, of course there are different tests in the pharmacy, you can buy and know exactly when you ovulate,
but in principle it is very difficult to determine or calculate, because fertilization itself occurs on the day of ovulation, plus or minus 3-5 days.
Any woman, having learned that she is pregnant, immediately goes to the most important specialist - a gynecologist. It is this doctor who examines the woman, prescribes tests and monitors the condition of the woman during the entire period of bearing the baby. In addition, the gynecologist determines what the gestational age is. And it turns out that for some reason it is more than the real one by as much as 2 weeks. Why does such a difference appear when determining the obstetric period of bearing a baby? Today we will try to figure it out.
Every woman who will soon become a mother tries to adhere to a balanced diet, significantly changes her lifestyle, giving up bad habits, visits doctors, takes the necessary tests, and so on. However, with all this, most of all women are interested in what is the gestational age.
What is the obstetric period for?
Pregnancy occurs when a woman's egg fuses with a man's sperm in the fallopian tube. In most cases, this date coincides with or with the day after it. Taking this into account, when calculating the period of bearing a baby from the day of ovulation, it is possible to determine the embryonic duration of the development of the unborn baby.
Although this method is not suitable in every case for subsequent monitoring of the course of pregnancy. And this is explained by the fact that ovulation does not always occur in the middle of the menstrual cycle.
In women without any deviations in the state of health, ovulation may begin earlier or later than the due date. And this is quite normal. That is why it is impossible to accurately calculate the embryonic period of a baby's development.
They began to determine the obstetric period a long time ago - in those days they did not even know about ovulation and how the pregnancy proceeds. Women determined that pregnancy had come by only one sign - they lost their menstruation. For this reason, they calculated the period of bearing a child, starting from the day of the last menstruation.
Modern specialists must take this period into account, since it is used to assess the state of growth and development of the fetus.
How is the obstetric term calculated?
It is well known that the baby is born after nine months. However, not all women know which months should be taken into account. A month is not an incomplete definition of the duration of bearing a baby. In this case, only the calculation made using the obstetric term is suitable. To do this, it is necessary to mark the last day of menstruation and count forty weeks or 280 days from it.
The onset of delivery is determined by various methods. For example, the first day of menstruation, which was the last, is taken, and 280 days are added to it.
However, experts consider this to be the surest way: 9 months and 7 days are added to the first day of menstruation - the resulting figure will be the date of birth. On this day, the period will be 40 weeks. However, this is an estimated date, since they can begin both at 38 weeks of gestation and at 42.
Who determines the obstetric term?
All dates necessary during pregnancy are calculated by an obstetrician-gynecologist.
Of course, many women do not understand how the calculation and basis for accounting for this gestational age is carried out. Do not panic if it does not coincide with the date that you calculated, since the obstetric period is used to monitor the progress of bearing the baby, prescribe the necessary examinations and important tests. Absolutely all future mothers are examined in identical terms.
In some cases, to specify the gestational age, women are sent to. However, this is not correct. On an ultrasound examination, the specialist assesses the stage of development of the child, based on the obstetric period, since it is he who is guided during all nine months. If during the ultrasound the data do not match, the doctor may prescribe a new examination.
It must be remembered that the first 14 days before the day of conception also play a special role. During this period, the woman's egg goes through the stage of preparation. Negative external or internal factors that can affect a woman's health can also affect the course of pregnancy. That is why the 2 weeks preceding the day of conception are also included in the obstetric period.
As you know, in most cases, it is quite difficult for young girls to establish the exact date of conception. That is why in medical practice, when determining the duration of pregnancy, they always started from the date of the beginning of the last menstruation preceding pregnancy. With this calculation, the so-called "obstetric" gestational age is established, which is slightly longer and differs from the real one.
How is the obstetric gestational age calculated?Many women who become pregnant for the first time do not know what the obstetric gestational age means and how to determine it. With a normal menstrual cycle (28 days), conception is possible on about day 14. Due to the fact that the date of the last menstruation is used in the calculation, the obstetric and embryonic (real) terms of pregnancy usually do not coincide. The run-up between them is the same 2 weeks, and sometimes 3.
How to calculate the embryonic (real) gestational age?
In order for a pregnant woman to independently calculate the actual gestational age, it is necessary to know the exact date of conception. If you can’t install it, then modern ones can come to the rescue. The design of such devices is based on electronic sensors that allow you to accurately determine the gestational age. The error in this case is small.
The situation is much easier when a woman remembers exactly the date of the last sexual contact. In this case, it is necessary to calculate only how many days have passed since that moment. The resulting number of weeks will be the actual gestational age.
How to correctly calculate the duration of your pregnancy?According to statistics, the difference between the real and obstetric period of 2 weeks is observed only in 20% of pregnant women. For another 20%, the difference between these two terms is less than 14 days. In the majority, 45%, the difference between 2 terms varies in the range of 2-3 weeks, and only in 15% of pregnant women is more than 3 weeks.
If the average duration of a woman's menstrual cycle differs from the standard 28 days, then fertilization does not occur on day 14, but a little earlier or later. Therefore, the embryonic period will differ sharply from that established by the gynecologist.
For example, if a woman's cycle lasts 35 days, then conception can only occur on day 21, and not as usual - on day 14. Therefore, the embryonic gestation period at 1 week of delay will be 5 weeks. At the same time, if you count from the last menstruation, then it will already be 6 weeks.
What to do if you can not determine the time yourself?In the early stages of pregnancy, it is possible to determine the period accurately enough only with the help of an analysis for. With its help, the approximate age of the fetus is established. In this case, the calculation is carried out from the date of the alleged conception. More accurately allows you to set the time of ultrasound. When conducting this study, the dimensions of individual parts of the fetal body are taken into account, according to which its age is established. According to the results of the ultrasound, it can be established as an obstetric gestational age, 
as well as embryonic.
When determining the gestational age, you can also take into account the duration of the cycle. Indeed, with a longer menstrual cycle, conception occurs a little later, therefore, childbirth will occur later.
Thus, knowing the main differences between the obstetric and embryonic gestational age, women will share these 2 concepts, and not be surprised that the period set by the gynecologist is longer than that expected by her, which is calculated according to the date of conception.