In all existing methods, the date of the last menstruation is used, therefore, even from an early age, doctors insist to remember or record both their beginning and end. Nowadays, medicine knows many ways by which you can find out the estimated date of birth of your child. Each of them has both advantages and disadvantages.
Determining the date of birth of the baby by the day of conception
The first way is to determine the estimated date of birth of the baby by the day of conception. Setting the date using this method is quite difficult, because not everyone knows the day of conception. Only a woman who has had only one sexual intercourse throughout the entire menstrual cycle can say this with confidence. If such information is not available, then the midpoint of ovulation – day 12 is considered the approximate day of conception. Sexual intercourse can be before ovulation, and after all, sperm can be viable in a woman’s body for 4 days, so this method is not entirely accurate. If a woman knows the date of maturation of her egg, then 280 days must be added to this number (this is the period of the entire pregnancy).
Definition by monthly
The second method is to determine the PDD (approximate date of birth) by monthly. Doctors use it most often. It is considered correct only when a woman has regular periods, and the cycle lasts 28 days. If so, then the Negele formula will come in handy. The meaning of this calculation is that you need to add 9 months and 7 days to the date of the last monthly period. There is also a simplified version: to calculate the PDR, we subtract 3 months from the first day of the last menstruation, and add 7 days to the resulting date. The error in this calculation may lie in the fact that women may have a menstrual cycle not 28 days, but more or less.
Definition by ultrasound diagnosis
Ultrasound diagnostics is one of the most accurate methods for determining the PDR. It can be used throughout the entire pregnancy. Since the fetus is visible on the monitor, the doctor can easily determine the day it will be born. At the first visit to an ultrasound scan for a period of 4-5 weeks, it is not as easy to establish a PDR as at the next 12 weeks. The age of the fetus does not always correspond to its size, there may be pathologies and deviations in development.
Determination by the degree of enlargement of the uterus
As soon as a woman has clear signs of pregnancy, most often she goes to a gynecologist for examination. The age of the fetus in this case is determined by the degree of increase in the uterus. This method is the most accurate, since the uterus grows every day. Also, the doctor can tell you the date of your last menstruation, if you do not have such information, and, accordingly, name the PDD.
Determination by the first movement of the fetus
If the expectant mother did not attend an ultrasound scan, then the estimated date of birth can be found by the first movement of the fetus. If this is the first child, then the fetus begins to move at 20 weeks. For those who give birth again, this period is 18 weeks. This method is not entirely accurate, because if the woman in labor is thin, then she can feel the first movements of the baby even at 16 weeks. Future mothers who lead an active lifestyle do not always remember this moment.
Definition by obstetric research
PDR is also determined during obstetric research. Once you are about 20 weeks pregnant, your abdominal volume and fundal height are measured at each visit to your gynecologist. This helps not only to determine the PDD, but also to detect pathologies in development in time. Doctors have known for a long time that certain numbers are characteristic of each gestational age, but only if the measurements were accurate.
As you can see, there are many ways to determine your baby’s estimated date of birth. Each of them has some errors, but they are mostly small. To keep the date as accurate as possible, we recommend using at least two methods.