Day of birth on the day of the last menstruation. How to calculate the expected due date

There are several ways to calculate due date.. However, oddly enough, only an experienced gynecologist-obstetrician can accurately determine the date of birth, since many factors, including heredity, influence the duration of bearing a child. By the way, the international community of gynecologists-obstetricians recently recognized a full-term pregnancy for a period of 38 weeks, and not just exactly 40 weeks.

In a word, even if you can, you should not relax. And within plus or minus two weeks from the appointed time, you need to be ready for childbirth, that is, collect the necessary things, sign an exchange card at the maternity hospital, talk to the doctor who will take delivery, if this is included in your plans.

Today, medicine knows many ways to calculate the date of birth. This can be done by the date of conception, by the date of ovulation, by the first day of the last menstruation before pregnancy, by the date of the first movement of the fetus. More precisely, the doctor can give the preliminary date of birth during an ultrasound examination (ultrasound) or during a gynecological examination, when measuring the size of the uterus. There are also so-called folk methods for calculating the date of birth, when the obstetrician can determine the date of birth by the future mother - the shape of her tummy and its omission-elevation. But here the experience of the midwife is very important, without which it is unlikely that it will be possible to calculate the date of birth. Yes, and this method “works” only on the eve of childbirth.

It is important to know!

The expectant mother needs to know that, according to statistics, only 4% of pregnant women give birth on the day that the doctor prescribed for them. That is why the date of birth, which appears on the exchange card, is called preliminary. So you should not worry if the birth began a few days or even weeks earlier. On average, pregnancy lasts 10 lunar months, that is, about 280 days. However, here everything is individual. As a rule, the date of birth is “determined” by the baby himself, when he finally matures and prepares for the birth.

The easiest way to calculate the preliminary date of birth (DDR) is by the day of conception. Unless, of course, you know exactly this significant day. If you know the date of conception, then just add 280 days to it - the duration of the average pregnancy and get the possible date of birth of the baby with variations of plus or minus two or three days.

Ovulation, that is, the day when the egg leaves the ovary, on average occurs on the 14th day of the menstrual cycle, although options are possible here. Determining the day of ovulation is quite simple, knowing the length of your monthly cycle and the first day of your last period. However, if the cycle is longer - 30 days, then ovulation will occur on the 15th. It is quite difficult to calculate this day if the cycle is inconsistent.

It is also necessary to take into account the fact that fertilization can occur within 2-5 days before or after ovulation, since spermatozoa can live this time in a woman's body. The easiest way to determine the day of ovulation is with the help of special tests that are sold in a pharmacy. So, knowing the day of ovulation, add 280 days to the date - the duration of pregnancy, and get the preliminary date of birth.

Define ovulation can be done using the website website.

As a rule, the date of pre-delivery is most often calculated from the first day of the last menstruation, adding 280 days to the date. Usually it is this date that the gynecologist writes down on the exchange card. Unless, of course, new circumstances were not revealed during the ultrasound.

You can also calculate the date of birth of a child like this: subtract 90 days (that is, 3 months) from the date of the last menstruation and add 7 days. For example, if the last cycle was on January 31, then the birth will occur approximately on November 7 of the same year.

This formula is good for those who have a regular menstrual cycle of 28 days. With a longer cycle, childbirth will come a little later, with a shorter one - a little earlier.

Another way to find out when your beloved baby will be born is by moving the baby. During the first pregnancy, the first tremors of the baby are usually at 18-20 weeks. Those who become mothers for the second time can feel the movements of the fetus at 16-18 weeks. To this date must be added 20 weeks for those who give birth for the first time, and 22 weeks for those who give birth again. This will be the date of birth of the child.

Of course, it often happens that a woman cannot name the exact date when she first felt the baby move. And this is the main problem with such a calculation.

Mom - under the nickname KATALINA shares her experience:

“In my first pregnancy, my mother calculated the date of birth by the first movement, and I gave birth right to the day :) Although the terms for menstruation and ultrasound were different. I remember moving at 18 weeks, and she seemed to add another 20 weeks. I know for sure that if you move at 16 weeks, then you need to add 22 weeks, if at 20 weeks, then add 18 weeks, at least that's how it was written in one of the magazines for parents.

According to gynecologists, the most accurate way to calculate the due date is an ultrasound. Already at the first ultrasound, which is usually done for up to 12-14 weeks, the doctor calculates the EDD, taking into account the size of the fetus, which in the early stages makes it possible to accurately determine the preliminary date of birth.

During pregnancy, during the first examination, the obstetrician-gynecologist, as a rule, immediately determines the gestational age, taking into account the degree of enlargement of the uterus. According to the gynecological scheme of the ratio of the gestational age and the size of the uterus, the doctor sets the PDR.
Then, after the 20th week of pregnancy, during each of your visits, the gynecologist will measure the height of the uterine fundus in order to monitor the rate of pregnancy and identify possible problems, since there should be certain indicators at each period.

When does a woman begin to be interested in the date of birth?

Then, when it comes time to prepare a dowry for the baby or when it comes time to go on maternity leave, to transfer all cases to colleagues for a while, and maybe much earlier, when only the expectant mother wants to influence the fate of her baby by planning his birth under a certain zodiac sign ?

One way or another, everyone is interested in determining the possible date of birth. In anticipation of changes in the composition of the family, you need to plan the time of holidays, the family budget, you may have to turn to future grandmothers for help.

From a medical point of view, the date of delivery is important when planning a caesarean section or for those women who will be calmer and more comfortable waiting for the moment of delivery in a hospital.

The abbreviation PDD means "estimated (planned) date of birth." It is worth paying attention to the fact that the date is precisely “estimated”.

No one can say for sure when your baby will decide to be born. But there are calculation formulas based on statistical data and the characteristics of female physiological cycles.

Many factors can affect the due date. Among them are the diseases of a woman, and the influence of ecology, and possible variations in the location of the placenta.

Important is the emotional state of the expectant mother and her age. But in the case of a normal pregnancy in a healthy young woman, the discrepancy between the actual date of birth and the calculated due date will be small (3-5 days).

Determination of the EDD by the date of the last menstruation

The Naegele formula, by which this calculation is made, is based on the fact that a normal pregnancy lasts 10 lunar months (280 days). Therefore, if a woman kept a monthly calendar and knew exactly their date, you need to count back 3 months, and then add another 7 days to the result:

EDD \u003d Date of menstruation - 3 months + 7 days

that is, if menstruation was on February 10, then counting back 3 months we get November 10, and adding 7 days we find out the PDR - November 17.

Calculation of EDD by ovulation

If you were planning a pregnancy and the date of conception, then you probably followed. allows you to determine. Adding 38 weeks (268 days) to this day, we get the possible date of birth.

ODD = Date of ovulation + 38 weeks.

How to calculate the estimated due date from the date of conception

If a woman knows exactly the date of sexual intercourse, which resulted in conception, another way to determine the date of birth can be offered. Physiologically, it is based on the same cycle as the basal temperature calculation, but does not require any preliminary measurements and charts.

EDD = date of conception + 266 days

That is, if sexual intercourse occurred on March 10, the expected date of birth will be November 22. The error of this formula is 3-5 days, it is associated with the period of life of a spermatozoon in a woman's body.

Determination of PDR during a medical examination is the most accurate method

If a woman registers for pregnancy in the early stages, then the condition and size of the uterus, the doctor will determine the duration of pregnancy and the approximate date of its completion (based on the "average" period of 40 weeks).

For a short period, the uterus is not yet palpable through the outer abdominal wall and a manual obstetric examination can tell about the period. But its characteristics are very subjective and depend on the qualifications of the doctor.

At 4 weeks, the uterus is the size of a chicken egg, by 8 weeks it will be larger - like a goose egg, and by 12 weeks it will reach the edge of the pubic bone.

An experienced obstetrician-gynecologist can determine the gestational age from these data.

Note that this technique works most accurately at the beginning of the first trimester. If a woman is not in a hurry for the first medical appointment, then there may be an error related to whether a large fetus is expected to appear, whether there is polyhydramnios, etc.

Planning the date of birth based on the results of ultrasound

During an ultrasound examination, it is possible to accurately determine the size of the fetus and its maturity. This will allow you to guess the date of birth.

Moreover, if you go for an examination in the first trimester and the gestational age is determined by the size of the fetal egg, then when you repeat, the doctor can tell you other data. This is not due to a mistake, just the intrauterine development of the baby is uneven.

The closer the due date, the more accurately you can determine the readiness of the child for birth.

For example, to plan hospitalization, preparation for a caesarean section.

Determination of the PDR by the date of the first movement

This method is less accurate than the previous ones, but is also physiologically justified.

All other formulas: calculation by the date of menstruation, ovulation or movement, are based on a standard 28-day cycle.

If a woman's menstrual cycle is less or more than 28 days, her physiological and metabolic processes may not fit into the calculated time frame. Moreover, there is not always a direct relationship here (that is, a woman who has a cycle of 25 days should not subtract 250 days from the date of the last menstruation instead of 280.

In any case, the calculation is carried out according to the standard formula. Just keep in mind that in your case, the likelihood of a baby being born a little earlier than the expected date increases).

The method with the greatest error - calculating the EDD by the date of the first movement - is further complicated by the fact that not every woman can accurately determine the moment of the first movement. The movements of the child are often mistaken for peristalsis or gases.

In addition to the objective calculation error, the date of birth can be affected by:

chronic diseases of a woman;
bad habits;
heredity;
or multiple pregnancy;
mother's age;
a cold or bacterial infection already during pregnancy;
repeated births;
fetal pathology;
stress.

As soon as she finds out about the pregnancy, the woman is already interested in the expected date of birth. After all, by this moment you need to prepare a dowry for a newborn, if necessary, provide yourself with assistants or pick up a nanny for older children, plan a family budget, taking into account replenishment of the family and a long vacation for the mother.

Someone is in a hurry by the time the baby is born to improve living conditions, make repairs or move closer to relatives. And all these issues need to be resolved by a specific date, the DA.

The methods for calculating the date of birth were very relevant, the calculation formulas were developed by obstetricians in different countries. With the advent of ultrasound, other methods with a large error began to be used less frequently. But they still arouse the interest of those who want to make a calculation without consulting a doctor, or at the stage of pregnancy planning.

The length of pregnancy from conception to birth is about 266 days, or 38 weeks. Since the date of conception is usually not known exactly, in modern obstetrics it is customary to calculate the gestational age from the first day of the last menstruation. With this calculation, it is approximately 280 days, or 40 weeks, since ovulation (the release of a mature egg from the ovaries) and, accordingly, fertilization usually occur about two weeks after the onset of menstruation. Turning to an obstetrician-gynecologist, many expectant mothers begin to worry about the difference in the date of birth - the one that the doctor calculated and the alleged woman herself. In order not to worry in vain, you need to know that there are two stages of pregnancy - obstetric and embryonic.

Embryonic term- this is the true gestational age from conception, it usually lags behind obstetric by about 2 weeks.

obstetric term doctors determine from the first day of the last menstruation before pregnancy. It should be remembered that all doctors use it: the size of the fetus, the timing of examinations, maternity leave and the date of birth are calculated taking into account only the obstetric gestational age. It is also very important to know the exact gestational age for screening for the presence of genetic abnormalities in the fetus (ultrasound and blood tests), since these examinations are carried out at strictly defined periods of pregnancy.

During the first visits to the antenatal clinic, the obstetrician-gynecologist usually determines the expected date of birth (ED). For this, several methods are used.

Method 1. Method for determining the date of birth by the date of the last menstruation

This is the most common way to calculate the PDR. To calculate your due date, subtract three months from your last menstrual period. You need to add 7 days to the resulting date - this number is the same estimated date of birth. Obstetrician-gynecologists, when calculating the PDR by this method, usually use special obstetric calendars, which greatly simplify the calculations.

However, it is far from always possible to accurately calculate the PDR only with the help of this method. This happens in cases where a woman has irregular menstruation, or in those patients who have a regular but long menstrual cycle. For example, if a woman has a typical cycle length of 35 days (and not 26-28, like most), then, most likely, she will only be able to conceive on about the 21st day of the cycle (and not on the 14th, as in a 28-day cycle). Accordingly, the EDD calculated by menstruation will be a week earlier than the actual expected date of birth.

Method 2. about the date of ovulation or the date of conception

If the date of conception is reliably known, then you can calculate the expected date of birth yourself by adding 266 days - this is the average gestation period. But even here there are nuances. You need to understand that even if a woman knows exactly the date of ovulation or the date of sexual intercourse, after which pregnancy occurred, this does not mean that she absolutely knows the date of conception. A spermatozoon that has entered the female body is capable of fertilization for an average of 4-5 days, sometimes even for a week, and a mature egg retains the ability to conceive for 2 days after ovulation. Therefore, even knowing exactly the date of sexual intercourse or ovulation, it is impossible to say with certainty that fertilization occurred on that day. It could have happened later. Therefore, the period calculated by ovulation or the date of conception cannot be considered absolutely accurate.

Method 3. Method for determining the date of birthon the first appearance at the antenatal clinic

Usually, the date of the upcoming birth and the gestational age are calculated by the doctor when registering for pregnancy. Doctors call this method of calculation - according to the "first appearance in the antenatal clinic." The gestational age, and, accordingly, the date of birth in this case is determined by the following parameters - the size of the uterus and the level of chorionic gonadotropin in the blood. Examining a woman in a gynecological chair, an obstetrician-gynecologist with both hands determines the size of the uterus. Most accurately, this method "works" in the early stages of pregnancy, up to about 12 weeks. The earliest period that can be determined by the size of the uterus is 5 weeks of pregnancy. By this time, the uterus is slightly enlarged, softened and becomes rounded. At later dates, the size of the uterus may vary slightly depending on the size of the fetus, the amount of amniotic fluid, and the structure of the woman's pelvis.

To determine the gestational age and calculate the approximate date of delivery in the early stages, a blood test for hCG (human chorionic gonadotropin) helps. It begins to be produced in the body of the expectant mother with the onset of pregnancy, and gradually, until about the 11th week of pregnancy, its amount increases and then decreases slightly. Determining the concentration of hCG in the blood at the beginning of pregnancy helps to accurately know its duration. Having received the results of a blood test for hCG, it is worth paying attention that in the laboratory tables, which determine the correspondence of the hormone level to the gestational age, the embryonic period is often indicated. That is, to determine the usual obstetric gestational age, 2 weeks should be added to the result obtained.

Method 4. Method for determining the date of birth about ultrasound

When performing ultrasound in early pregnancy, measuring the size of the fetal egg and embryo, the gestational age can be determined with great accuracy. At 4–5 weeks, a small “black circle” is determined in the uterus during an ultrasound examination - this is a fetal egg, in which an embryo will appear a little later. At about 6-7 weeks, the embryo appears in the form of a small "stripe", and you can see its heartbeat. More accurate is the period calculated by measuring the KTR of the embryo (KTR is the coccygeal-parietal size, that is, the maximum distance from the fetal head to its tailbone). After 12 weeks, the gestational age is determined by ultrasound by measuring the various sizes of the head and abdomen of the fetus, the length of its arms, legs, etc.

Until 9-10 weeks of pregnancy, the embryo grows proportionally, and its size in all women with the same gestational age will be approximately identical. In the future, these indicators will differ for expectant mothers of different nationalities, with different body weights, the weight of mom and dad at birth will also matter, and so on. That is, in the later stages of pregnancy, normally developing children of the same “age” may have different sizes (fluctuations can be about 2 weeks and sometimes even more), and in such a situation, it is impossible to reliably determine the gestational age according to ultrasound data.

Method 5. Method for determining the date of birthabout the first fetal movement

We note right away that this method of determining the PDR has recently been used less and less. It is based on the fact that women who are carrying their first child begin to feel his first movements on average at about 20 weeks of pregnancy, and pregnant women for the second or more times, a little earlier, at 18 weeks. That is why obstetrician-gynecologists recommend that the expectant mother remember the date of the first fetal movement and enter this data into the exchange card. To calculate the expected date of birth for women preparing to become a mother for the first time, 20 weeks must be added to the date of the first fetal movement, and for those expecting a second baby - 22 weeks.

However, this method of determining the date of the upcoming birth is often erroneous. What is the matter here? The problem is that the time when a woman can feel the first movements of the fetus is very individual and depends on her sensitivity, physique, as well as employment and experience. So, some expectant mothers feel the first movements already at 15–16 weeks, and someone only after 20. Slender women, as a rule, begin to feel them earlier than full ones. Expectant mothers who lead an active lifestyle, work hard, usually feel the movements of the fetus later than those who are less busy and have more opportunity to listen to their inner feelings. Pregnant women for the second or more times already know exactly how the baby's movements are felt, therefore, as a rule, they recognize the movements of the crumbs earlier than "inexperienced" primiparous women, who often mistake fetal movements for increased intestinal motility and gases.

All of the above methods allow you to calculate the estimated date of birth. However, it must be remembered that, of course, it is not absolutely accurate. It is not uncommon for a pregnancy to endure or be premature. To provoke the onset of premature labor can be deviations in the development of the fetus, pathological processes in the body of the expectant mother, stressful situations, hereditary factors and many other reasons. Therefore, it is very important to realize that the calculation of the date of birth is a very conditional concept, regardless of the method used, and it is not possible to predict exactly when the baby will be born.

How is the estimated date of delivery for IVF calculated?

In the case of IVF (in vitro fertilization), the fertilization of an egg with a spermatozoon is carried out "in vitro" by an embryologist. Embryos develop in the laboratory for 3-5 days, after which they are transferred to the uterus. Doctors calculate the true term of pregnancy after IVF from the date of ovarian puncture, that is, a procedure when a special needle is used to take the follicular fluid and the follicles contained in it for subsequent fertilization “in vitro”, and to determine the “usual” obstetric period, 2 weeks are added to the date of ovarian puncture.

If the transfer of the embryo to the uterus was preceded by its cryopreservation (that is, freezing in liquid nitrogen), to determine the exact gestational age, doctors add 5 days to the transfer date (this is the number of days the embryo develops before freezing), and to determine the obstetric period, add 2 to the received true period weeks, and calculate the date of birth.

Having learned that a baby will appear in about 9 months, the expectant mother seeks to find out the exact date of the joyful event. I want to meet the long-awaited new family member ready mentally and physically.

Gynecologists calculate the expected duration of relief from the burden in many ways. Usually the birth of a child occurs at 38-42 weeks of pregnancy.. Examination by a doctor, ultrasound data, date of ovulation - this is information that helps to calculate the future "day X".

by the most simple and popular is the calculation at the beginning of the cycle of the last menstruation. This is a simple method by which the estimated date of birth (ED) is determined. It is called the obstetric method. But, like other calculations, it shows an approximate date.

Obstetric calculations serve as the basis for taking tests, they issue a certificate of the beginning of maternity leave, and calculate the PDR. They will help you find out the date of birth by the last menstruation.

It is easy to find out the date of birth by the last menstruation. However according to statistics, only 4 out of 100 women give birth at the appointed time. For the rest, this figure fluctuates within 2 weeks in one direction or another.

Obstetric method for determining the date of birth

Using the obstetric method, the date is calculated at the beginning of the cycle of the last menstruation. Best suited for women with regular periods.

Obstetric calculations serve as the basis for taking tests, they issue a certificate of the beginning of maternity leave, and calculate the PDR.

The PDD by this method is found as follows:

3 months are subtracted from the start date of the last cycle;
7 days are added to the result;
the resulting number is the desired PDR.

This date is very important at the initial stage of pregnancy for the doctor and for the woman in labor.

It allows the doctor to:

control the process of pregnancy;
monitor the development of the fetus and the health of the woman;
to prevent or notice pathological changes in time;
determine the maturity of the fetus, taking into account the indications of ultrasound and other examinations;
prepare a woman psychologically, choose the method of childbirth, taking into account the maturity of the fetus and the health of the expectant mother.

Knowing the due date helps a woman:

find out the date of birth (according to the last menstruation) at the very beginning of pregnancy and compare with your further feelings;
adjust it with the doctor if necessary;
get a certificate for maternity leave in time at the antenatal clinic;
discuss with the doctor the term of childbirth and obstetric care, based on medical indications.

Knowing the DA helps the expectant mother to properly prepare for the upcoming important event, to fulfill the requirements of the doctor at every stage, which will strengthen the health of the woman and child.

How to determine the date of birth using the Negele formula

The Negele formula, a well-known German obstetrician, is used in the obstetric method for determining the PDR.

Of course, each organism is individual, but there is an average obstetric duration of pregnancy. 280 days are taken as a basis, based on the average cycle length (28 days). This correlates with the phases of the moon, so they say that pregnancy lasts 10 lunar months.

Pay attention to the advice of doctors

According to the formula, 9 months are added to the first day of the last menstruation, then another 7 days are added. With the obstetric method, 3 previous months are taken away and 7 days are added. This is the so-called inverse Negele formula.

This simple formula will help you find out the date of birth by the last menstruation.

A similar calculation of the PDR has been used in practice for many years, error is up to 2 weeks, but additional examinations help to significantly reduce it.

Important to remember! It is very important to find out the date of birth using the data on the last menstruation. This must be done as early as possible so as not to give birth in unsuitable conditions (if the term was determined incorrectly). The health of the woman in labor and the child, payments and the period of maternity leave depend on this.

Online calculator for determining the date of birth

These calculators help you quickly calculate the required date. They are built using the same Negele formula. By entering the required numbers in the required columns and clicking with the mouse, the estimated date is obtained.

But for a more accurate result and the correct course of pregnancy, additional examinations are required to help clarify the PDR.

Everything is convenient and fast. But for a more accurate result and the correct course of pregnancy, additional examinations are required to help clarify the PDR.

How accurate is the due date?

Cycle time and PDR are related. The initial calculation is based on a cycle (28 days). With a longer, irregular or shorter cycle, there will always be deviations. So the number that the doctor determines using this method is only the estimated date of onset of labor.

The error will help to reduce the data of tests, examinations by a gynecologist in consultation, monitoring the course of pregnancy.

Interesting fact! The date of birth of a child depends on various reasons, it can be changed by illness, stress, the expectation of twins. If twins or triplets are born, then this happens ahead of time. In this case, gynecologists consider this the norm.

Other ways to find out the date of birth

Having calculated the PDR, the doctor will closely monitor the health of the future woman in labor and the fetus. The duration of pregnancy is largely determined by the individual characteristics of the mother and child. To take into account all factors and reduce the likelihood of error, the gynecologist constantly analyzes data from various studies.

To find out the date of onset of childbirth, gynecologists use not only the calculation of the last menstruation, but also a number of other methods:

ultrasound procedure;
accounting for the first movement;
embryonic method of calculation (ovulation, day of conception);
gynecological examination.

All these methods give the doctor additional information about the actual gestational age, fetal maturity, and readiness for childbirth.

All methods are not absolute. So, a woman giving birth for the first time will feel the movement of the fetus in the middle of the term. A woman who has already given birth will feel the movement of the fetus much earlier, because she expects this and listens to herself more carefully. Ovulation does not necessarily correspond to the day of conception, and the height of the uterine fundus is a rather individual indicator.

Don't miss out on these helpful tips:

However the totality of data allows the specialist to determine the onset of childbirth within 1-3 days. Ultrasound is considered the most accurate at 11-14 weeks.

Important to remember! All methods are not absolute. So, a woman giving birth for the first time will feel the movement of the fetus in the middle of the term. A woman who has already given birth will feel the movement of the fetus much earlier, because she expects this and listens to herself more carefully.

Note! The duration of the menstrual cycle has a direct impact on the timing of childbirth. They are directly related. In the case of a shorter cycle, childbirth will occur earlier than the calculated number. If the cycle is longer, then the event will occur later, although in both cases these will be healthy full-term babies.

In order for the pregnancy to proceed without complications, the expectant mother should immediately be registered. A gynecologist will help a woman correctly determine the period and will accompany her at all stages of pregnancy. Knowing the date of birth will help a woman properly prepare for the birth of a baby and become a happy mother of a healthy child.

How to find out the gestational age, knowing the date of the last menstruation:

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The expected date of birth begins to interest a woman from the first day she found out about her situation. The approximate birthday of a child can be calculated in several ways, but none of them can boast of 100% accuracy. Many factors can influence the pregnancy process, and delivery is often premature or late.

What determines the time of birth

Even in a healthy woman carrying a healthy baby, the date of birth may deviate from the approximately calculated period and depends on:

on whether she gives birth in or;
from the duration of the menstrual cycle;
from heredity and other individual characteristics of the mother;
on the characteristics of the intrauterine development of the baby;
on how many babies are in the uterus.

In the presence of chronic diseases in a woman, a violation of the intrauterine development of a child, acute diseases or injuries during pregnancy, the delivery date may significantly deviate from the planned date.

Ways to determine the date of birth

The most common methods for determining the estimated due date are as follows:

by the date of the last menstruation;
by the time of ovulation;
by date of conception;
by ultrasound;
according to the size of the uterus;
by the first movement of the fetus.

Let's consider each in more detail.

By last menstrual date

The date of birth by menstruation is the most common way to determine.

It has been used by obstetrician-gynecologists for many decades because:

not all pregnant women know the time of the last ovulation or the date of conception with regular sex life, but everyone remembers when they had their last menstruation;
this is a pretty accurate method.

To determine the day of birth, it is necessary to remember the first day of the last menstruation, add 1 year to this date, then subtract 3 months, and then add 1 week. The calculated date will be a guideline for the expected birth. Another way to determine: add 9 months and 1 week to the first day of the last menstruation.

By time of ovulation or expected conception

The method of calculating the date of birth by the date of conception can be used with a planned pregnancy, when a woman specifically calculated the days of ovulation and knows them. It is during this period that conception occurs. 266 days are added to the first day of ovulation and the date of delivery is calculated according to the calendar. This method is called embryonic.

By date of intercourse

This method is convenient to use with irregular or rare sexual activity. In this case, the woman knows which day in her life was decisive. Everything is very simple - 266 days are added to this date. This method is closer to the embryonic one. The due dates calculated by these two methods may differ by only a few days because the date of intercourse and conception often do not coincide. Not everyone knows that some spermatozoa are able to live in a woman's body for up to 9 days, waiting in the wings.

According to ultrasound

Using ultrasound, the doctor can determine the approximate date of birth, based on the established age of the fetus. Most precisely, this is established in the first trimester of pregnancy. In the future, there may be an error from several days to 3 weeks.

According to the size of the uterus

An old medical method was an approximate determination of the gestational age and, accordingly, the expected birth according to the size of the uterus. As in the previous case, it is possible to more accurately set the time of delivery in the early stages of pregnancy. In the future, the size of the uterus depends on many factors (the size of the fetus, the amount of water). In addition, this method is only suitable if there is 1 child in the uterus.

By the first movement of the fetus

An old folk way of guessing the date of birth is to move the baby. After the disappearance of menstruation, a woman could only suspect that she was pregnant, but when the fetus began to move, this was a 100% sign.

The woman added 20 weeks to this date and could quite accurately guess the due date with minor errors. It should be borne in mind that multiparous people are already familiar with the feeling of fetal movement in the uterus and they, as a rule, feel it 1-2 weeks earlier than primiparas.

Calculation efficiency

The exact day of delivery cannot be determined, because the period from 38 to 42 weeks of pregnancy is considered the normal period for delivery. Thus, as many as 28 days can be considered the date of delivery "at term". However, in the normal course of pregnancy, different methods of calculation approximately coincide and circle around the same date in the range of +/- 14 days.

Gynecologists officially still use the calculations for determining the possible day of birth according to the last menstruation, therefore this period is called obstetric. This method in about 20% of cases guesses the date of birth with an accuracy of +/- 5 days, and this is a rather high percentage. The exact coincidence of the date of birth and the obstetric period is about 5%.

How do the features of the menstrual cycle affect the date of birth

Regardless of the duration of the menstrual cycle, the obstetrician-gynecologist applies the formula for calculating the term of childbirth by the date of the last menstruation. Accordingly, women with a short cycle and a long one will have the same due date. However, the date of ovulation is different for them, therefore, the conception and the term of delivery will be different.

With a short menstrual cycle (24 days) ovulation occurs on the tenth day. Fertilization occurs on the days of ovulation. Therefore, the actual due date in women with a short cycle will be expected a week earlier. The date of birth is calculated using the following formula: the date of the first day of the last menstruation plus 1 year and minus 3 months.

Long cycle (35 days) ovulation occurs on the twenty-first day. Childbirth will be a week later than the gynecologist calculated. A woman can calculate the date in this way: the date of the first day of the last menstruation, plus 1 year, minus 3 months, and plus 14 days.

Calculate the date of birth with an irregular menstrual cycle with large jumps should be according to the classical formula.

When you can not use the obstetric method of calculation

The obstetric method of determining the date of birth by the last menstruation is the most common.

But it is not possible to use it in the following cases:

when pregnancy occurs immediately after a previous birth, and menstruation has not yet occurred;
with severe menstrual irregularities, when the interval between periods can be more than a few months, as is the case with menopause or various female diseases, such as polycystic ovaries or hormonal disorders.

What are the deviations from the deadlines?

The bearing of a child lasts 9 calendar months, or 10 lunar months (28 days each), or 280 days.

Births are classified into urgent, premature and late:

Childbirth at 38-42 weeks is a normal period. Statistically, 70% of mothers give birth in the range of 39-41 weeks. Primiparas often give birth 1 week later than the normal due date. But with repeated births, on the contrary, women often give birth before 39 weeks.
Childbirth after 42 weeks is late. The child is considered to be overdue. There are about 9% of such births.
Childbirth before 38 weeks is premature. The viability of the baby depends on the gestational age at delivery. The closer this period is to normal, the better.

Everything is individual, and in case of premature birth, a completely healthy and mature baby can be born, more often this happens for a period exceeding 35 weeks. If the baby is underweight - less than 2500 grams, he will be considered premature.

The second degree of prematurity is established at the term of delivery from 32 to 35 weeks and the weight of the child is less than 2000 grams. However, he also has a very high chance of "ripening" and gaining weight after birth without the use of hardware life support.

In case of premature birth from 28 to 31 weeks, the child will be with prematurity of the 3rd degree and low body weight (from 1000 to 1500 g). Such children are successfully nursed in perinatal centers.

At the birth of a child for a period of 22-28 weeks, he will have a 4th degree of prematurity. The baby has extremely low body weight and undeveloped lungs. There is no surfactant substance, which ensures the free breathing of the child.

Previously, a fetus weighing 700 g was considered viable, now - with a mass of 500 g or more. Such children are nursed in intensive care units using special plastic transparent boxes - incubators, which provide the necessary temperature, humidity and sterility of the environment. The baby is connected to a ventilator, feeding is carried out intravenously or through a tube, the necessary drug therapy is provided.

A child born before 22 weeks will be unviable due to severe immaturity. Such babies are currently not able to leave the medicine.

Causes of preterm labor

The total share of all preterm births accounts for about 10% of cases. The cause may be maternal or fetal pathology, or a combination of various factors.

The most common of them:

Social and domestic - smoking, alcohol abuse, drug use, stress, extreme physical activity, malnutrition and hypovitaminosis.
Pathology of the uterus - the consequences of abortion, other operations on the uterus, hypoplasia, endometritis, endometriosis.
Pathology of ongoing pregnancy - placental abruption, oligohydramnios, premature rupture of amniotic fluid, inflammation of the membranes, multiple pregnancy,.
Mother's diseases - diabetes mellitus, hypertension, rheumatism, bronchial asthma, severe anemia, mental disorders, etc.
Multiple anomalies in the development of the child, incompatible with life, at present, the latter is rarely the cause of premature birth, as women try to terminate their pregnancy in the early stages for medical reasons.

In the presence of such risk factors, a woman should be especially careful, since she has a high risk of having a premature baby. She may have to spend some time saving.

Determining the expected date of delivery is an important task. But in any case, the calculated period is approximate. It depends on many reasons. Therefore, with a long gestational age, a woman should listen to herself and expect childbirth, starting from the 37th week of pregnancy, or even earlier.