Many women, when they learn about their pregnancy, begin to experience a variety of feelings - some are overwhelmed with joy, others feel confused. And, of course, every future mother has many questions. They are especially interested in the day of the birth of their child.
There are many ways to calculate the estimated date of delivery. Consider them.
Calculate childbirth by date of conception
It has been established that conception is possible only during ovulation, when a mature egg leaves the follicle to meet with the spermatozoon. Ovulation usually occurs on the 14th day of the menstrual cycle (the period starting from the first day of the beginning of menstruation and ending on the first day of the beginning of the next). The duration of the menstrual cycle for each woman is different. It may be 28-35 days. On average, it lasts 28-29 days.
A woman planning a pregnancy or following her cycle can accurately determine the day of ovulation. In addition, during this period there are signs characteristic of it.
It is worth noting that the day of sexual intercourse may not coincide with the day of conception, since the viability of individual spermatozoa in a woman’s body can be up to 3 days.
So, knowing the day of ovulation, you can quite accurately calculate the date of birth of the child. You just need to add to this day 280 days (the average duration of pregnancy). Consider that in this way a woman can only calculate the period of birth of a baby with only a constant menstrual cycle.
Calculate the date of delivery by monthly
Usually, gynecologists use this method, it is called obstetric term. When registering, the doctor will certainly ask the woman when she had her last menstruation. And, to calculate the day of birth, he will use the formula invented by the German obstetrician FK Negele: from 1 day of the beginning of the last menstrual period 3 calendar months are taken away and 7 days are added. It is important to note that if the menstrual cycle is not 28 days, then this method of calculation is rather oriented.
birth day by fetal movement
This method is not accurate. The error can be up to 2 weeks. But nevertheless, the future mother will have an idea when her baby is approximately born. So, the woman can feel the first movement of the fetus at the first pregnancy at 20 weeks, with the second at 18 weeks. It is known that it lasts 40 weeks. It turns out, to find out the approximate date of birth, you need to add to the date of the first stirring 20 weeks or 22 weeks.
With the help of all the above methods, it is impossible to calculate the child's birthday alas. Many factors can affect this. These include various diseases (polyhydramnios, diabetes mellitus, preeclampsia, multiple pregnancies, genetic features, menstrual irregularities, and others). According to statistics, only 10% of babies are born at that time, which the doctor set when registering. Therefore, it is impossible to accurately calculate the date of birth, you can only figure out approximately when the child will be born.
Method 1. The method of determining the date of birth by the date of the last menstruation
This is the most common way to calculate the DA. To calculate the date of birth from the date of the start of the last menstruation, you need to subtract three months. To the resulting date you need to add 7 days - this number is the very estimated date of delivery. Obstetricians and gynecologists, making calculations of the DA by this method, usually use special obstetric calendars, which greatly simplify the calculations.
However, it is not always possible to accurately calculate the DA only with the help of this method. This happens in cases when 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 duration of 35 days (rather than 26–28, like most), then, most likely, her conception will be possible only on about the 21st day of the cycle (and not on the 14th, as with the 28-day cycle). Accordingly, the DA, calculated for menstruation, will be a week earlier than the actual estimated date of delivery.
Method 2. The method of determining the date of birth p o the date of ovulation or the date of conception
If the date of conception is reliably known, then it is possible to calculate the expected date of birth independently, by adding 266 days - this is how much the average period of gestation is. But here there are some nuances. You need to understand that even if a woman knows for sure the date of ovulation or the date of sexual contact after which the pregnancy occurred, it does not mean that she absolutely knows the date of conception. A sperm cell that has entered the female body is capable of fertilization on average for 4–5 days, sometimes even during the week, and a mature egg retains the ability to conceive within 2 days after ovulation. Therefore, even knowing exactly the date of sexual contact or ovulation, it is impossible to say with certainty that fertilization took place on this very day. It could happen later. Therefore, the term calculated by ovulation or the date of conception, can not be considered absolutely accurate.
Method 3. The method of determining the date of birth at the first appearance in the antenatal clinic
Usually, the date of the upcoming delivery and the period of pregnancy are calculated by the doctor when registering for pregnancy. Doctors call this method of calculation - on the "first appearance in the antenatal clinic." Gestational age, and, respectively, the date of birth in this case is determined by the following parameters - the size of the uterus and the level of human chorionic gonadotropin in the blood. Examining a woman in a gynecological chair, an obstetrician-gynecologist uses two hands to determine the size of the uterus. Most accurately, this method "works" in early pregnancy, up to about 12 weeks. The earliest period, which can be determined by the size of the uterus, is 5 weeks of pregnancy. By this time, the uterus increases slightly, softens and becomes rounded. In later periods, the size of the uterus may vary slightly depending on the size of the fetus, the amount of amniotic fluid, and the pelvic structure of the woman.
A blood test for hCG (human chorionic gonadotropin) helps to determine the duration of pregnancy and to calculate the approximate date of delivery in the early stages. It begins to be produced in the body of the future mother with the onset of pregnancy, and gradually, approximately until the 11th week of pregnancy, its number increases, and then decreases slightly. Determining the concentration of hCG in the blood at the beginning of a pregnancy helps to know its duration fairly accurately. Having received the results of the blood test for hCG, it is worth noting that the laboratory tables, which determine the compliance of the hormone level with the gestational age, often indicate the embryonic period. That is, to determine the usual obstetric period of pregnancy to the result obtained, add 2 weeks.
Method 4. The method of determining the date of birth of the ultrasound
When conducting ultrasound in early pregnancy, measuring the size of the ovum and the embryo, the duration of pregnancy can be determined with great accuracy. At 4–5 weeks, a small “black circle” is determined by ultrasound in the uterus - this is the ovum in which the embryo will appear a little later. At about 6–7 weeks, an embryo appears in the form of a small “strip”, and its heartbeat can be seen. The term calculated by measuring the CTE of an embryo is considered more accurate (CTE is the coccyx parietal size, that is, the maximum distance from the head of the fetus to its coccyx). After 12 weeks, the duration of gestation with ultrasound is determined by measuring the different sizes of the head and abdomen of the fetus, the lengths of its arms, legs, etc.
Up to 9–10 weeks of pregnancy, the embryo grows in proportion, and its size in all women with the same gestational age will be approximately identical. In the future, these indicators will differ in future mothers of different nationalities, with different body weight, 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” can have different sizes (fluctuations can be about 2 weeks and sometimes even more), and in such a situation, the gestational age of the ultrasound data cannot be reliably determined.
Method 5. The method of determining the date of birth of the first movement of the fetus
We note immediately that this method of determining the DA in recent times is becoming increasingly rare. It is based on the fact that women who are bearing their first child begin to feel his first movements at an average of about 20 weeks of gestation, and pregnant women a second or more times - a little earlier, at 18 weeks. That is why doctors obstetricians and gynecologists recommend the expectant mother to remember the date of the first movement of the fetus and enter this data into the exchange card. To calculate the expected date of birth for women who are preparing to become a mother for the first time, you must add 20 weeks to the date of the first movement of the fetus, and 22 weeks for those who are waiting for the second baby.
However, this method of determining the date of the upcoming delivery is often erroneous. What is the matter? 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, build, as well as on employment and experience. So, some future mothers feel the first movements already in 15-16 weeks, and someone only after 20. Slender women, as a rule, begin to feel them earlier than full ones. Future moms who lead an active lifestyle, work a lot, usually feel the movement of the fetus later than those who are employed less and have more opportunity to listen to their inner feelings. Pregnant women, for the second and more times, already know how exactly babies move, therefore, as a rule, they recognize crumbs before the “inexperienced” primiparous women, who often take fetal movements for increased intestinal motility and gases.
All the above methods allow you to calculate the estimated date of delivery. However, we must remember that, of course, it is not absolutely accurate. Often there is postponing or premature pregnancy. Deviations in fetal development, pathological processes in the future mother's body, stressful situations, hereditary factors and many other reasons can provoke the onset of premature labor. 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.
What is the estimated date of delivery for IVF?
In the case of IVF (in vitro fertilization), the fertilization of the egg by the spermatozoon is performed “in vitro” by an embryologist. Embryos develop in the laboratory for 3–5 days, after which they are transferred to the uterus. Doctors reckon on the true duration of pregnancy that occurs after IVF from the date of the puncture of the ovaries, that is, procedures when the follicular fluid and follicles contained in it are taken with a special needle for in vitro fertilization, and 2 weeks are added to determine the “usual” obstetric period to the date of ovarian puncture.
If the embryo is transferred to the uterus before it is cryopreserved (i.e. freezing in liquid nitrogen), physicians add 5 days to the date of transfer (this is the number of days the embryo develops before freezing), and to determine the obstetric period, 2 weeks, and calculate the date of delivery.