Almost immediately after a positive pregnancy test result, women start thinking about when to give birth. This date is important as a landmark, a direction that will help you better understand how much is still left, as well as plan things and prepare for the birth of a baby. The expected date of delivery is also important for doctors. There are several ways to calculate it - by the last menstruation, by the date of conception, by ovulation... How to do this in practice, this article will tell.
PDR - what is it and why count?
The expected date of birth is considered not only so that future parents can check with the "Saints" and choose a name for the child, but also plan father's vacation. PDD is an important landmark that is necessary for the attending physician and the woman herself to track the dynamics of pregnancy, to plan the method and method of delivery.
The estimated due date is not accurate, so you shouldn't treat it as your baby's date of birth. When the day of birth comes, medicine, alas, cannot predict in advance. Childbirth is a very complex and multi-stage physiological and biochemical process, for the beginning of which the complete readiness of both the mother and the fetus is required. And you need to calculate the PDR only in order to know the approximate time period in which the day of birth will happen.
Normally, full-term babies are born between 38 and 42 weeks of gestation inclusive. The due date may fall on any of the days during this time. Only every twentieth baby is born strictly in the PDR, the rest prefer to surprise their parents with their birth either earlier or later than the date indicated in the mother's exchange card as PDR.
Counting method
You can make the necessary calculation in two ways - on your own with a calculator and a calendar, or using a pregnancy calculator that works online. The calculator will help you save time, since it allows you to calculate the required date in seconds. The calculation algorithm is the same both for self-calculations and when using a calculator. It is based on the obstetric method for calculating the gestational age.
This means that it is accepted to consider the PDR not from any day, but from the first day of the last menstruation. This calculation is considered the most correct method. The fact is that the day of the beginning of the last menstruation before the onset of the "interesting position" is the only precisely known date, and it is simply impossible to determine all the rest with an accuracy of the day. The gestational age according to obstetric standards is calculated from the first day of menstruation, considering this day as the first day of pregnancy.
It is easy to calculate the due date from the last menstruation. To do this, you can use one of the obstetric formulas:
- 9 calendar months are added to the day of the beginning of the last menstruation and 7 days are subtracted;
- from the day of the beginning of the last menstruation, subtract 3 months and add 7 days;
- 280 days are added to the day of the beginning of the last menstruation (the average duration of bearing a fetus in a person).
Using an online calculator, the calculation does not take much time... A woman simply enters the day of the beginning of the last menstruation and receives free information about how many days are left before childbirth, what date the end of the 40th week falls on (this is the PDR), how long the woman is now (with an accuracy of a week and a day). The calculator will also facilitate the task of finding information about the due date - it will give useful links to articles on the development of the baby, remind you when you need to consult a consultation, what tests to take, when to appear for the first or second prenatal screening.
How to calculate the date of birth by the date of conception is a difficult question. The fact is that it is extremely difficult to establish the exact date of conception, even if the woman knows for sure which sexual act led to the birth of a new life. Fertilization itself occurs only during the ovulatory phase... It does not last long - from 24 to 36 hours after the release of the egg. It is this life expectancy that is assigned to the female reproductive cells.
Spermatozoa are more persistent and hardy and can exist in the genital tract of a woman for up to 3-5 days, and therefore after the egg leaves the follicle on the surface of the ovary, it can be fertilized as those germ cells that were already in the genital tract after the act in 3 -4 days before ovulation and sperm from the "fresh batch".
Ovulation itself is also a very unstable date, it can happen a little earlier or later a few days, since this process is directly dependent on the endocrine background.
If a woman thinks she knows the date of conception because she remembers the day of intercourse, this does not mean at all that fertilization itself took place on that very day. For this reason, the date of birth is not calculated from the date of conception. But you can also calculate by the date of ovulation (if you know it for sure) - 266 days are added to it. This allows you to find out what day the expected day of birth falls on.
Neither doctors nor calculators use such a calculation system due to its high inaccuracy and inaccuracy.
Irregular cycle and IVF
It is quite difficult to use a calculator and independent calculations if a woman has such an irregular cycle that she simply does not remember when her last period began. Irregular cycles can be different. If they manifest themselves with different duration of cycles (then 28, then 32 days), this will not affect the calculations, since the date of the last menstruation is there, the rest can be calculated without problems.
If the date is unknown, then in the early stages you need to do Ultrasound to determine the gestational age. Only up to the 10th week of pregnancy, it can be determined with fairly high accuracy. Until this time, the processes of embryogenesis take place, when organs, tissues, systems are laid in the baby, and the growth of different embryos during this period proceeds at approximately the same pace.
By the end of the first trimester, babies in the womb begin to grow in different ways: some are larger, others are small. This is influenced by the genetic program received by the baby from the parents, or simply heredity. Determining the term by the size of the fetus becomes difficult.
If the desired pregnancy has occurred in the IVF treatment protocol, general calculators and calculation methods for pregnant women are also not suitable. For artificial insemination in a woman, drug superovulation is provoked, and then several mature eggs are taken from several follicles at once by the method of follicular puncture. Fertilization with the sperm of the husband or donor takes place in the laboratory. After a few days, the embryos are transferred to the patient's uterus.
After 14 and 21 days after this, a woman can visit an ultrasound specialist to confirm or deny the fact of pregnancy. In this case, it will also not be possible to count from conception, because conception was in the laboratory. It all depends on how large the embryos were transferred when they were implanted.
There are special calculators that help calculate the due date and current term for women after IVF. They need to indicate the date of the embryo transfer, as well as the age of the embryos at the time of transfer (three days, four days, five days). As a result, they receive a calculation in which the gestational age is indicated in the obstetric period, and the PDD, like everyone else, occurs at the end of the 40th week of pregnancy.
What should be considered?
When determining the due date by any of the methods described above, a woman should remember that there are a number of personal characteristics of the body that can also affect the PDD. The calculations, of course, will remain the same, you do not need to make any adjustments in them, but you should know that women with a short menstrual cycle usually give birth earlier than the expected date. With a long cycle (more than 33 days), there is a high probability that the pregnancy will also be prolonged to 42 weeks or more.
Women with an established cycle, lasting from 28 to 30 days, usually give birth as close to the expected day of birth.... This is the classic obstetric standard for menstrual cycle length.
If a woman is expecting her first child, then childbirth most often also approaches the date defined as PDD. And with repeated births, the likelihood is higher that the child will want to be born earlier than the date indicated in the mother's exchange card.
Multiple pregnancies usually end with childbirth before PDD. Large babies are in no hurry to be born, so labor may start later than expected.
Relative confidence in the timing can only be in women who, for medical reasons, have a planned caesarean section. Its term is appointed for 39 full weeks, if there are no circumstances and reasons for an earlier delivery. In this case, the expectant mother can choose her child's birthday in the specified time period on her own, doctors give this opportunity, offering a choice of any day between 39 and 40 weeks.
For information on how to calculate the gestational age in weeks and calculate the due date from the last menstrual period, see the next video.
