To calculate the date of delivery, you only need to know the date of your last menstrual period and the length of your menstrual cycle. Using this data, you can calculate the expected date of delivery and due date. The Naegele rule will also help.
What is the Naegele method for due date?
This method is based on the assumption that each pregnancy lasts 280 days (9 months), a cycle of 28 days, and fertilization occurred exactly on the 14th day of the menstrual cycle. Interestingly, it counts pregnancy from the first day of the last menstruation, so the age of pregnancy is always 2 weeks more than the pregnancy calculated from the day of conception. However, there is no reason to worry – every doctor uses this method.
As you can see, unfortunately, Naegele’s method is not perfect, because it does not take into account the fact that some of us have an irregular period or last longer or shorter than 28 days in books. Thus, the moment of ovulation is completely different. Fertilization itself does not always take place exactly on the day of ovulation. Therefore, when determining the date of delivery, the doctor usually also takes into account the results of ultrasound from the first trimester of pregnancy, where this date is calculated on the basis of individual features of fetal development.
Appointment of the day of ovulation
The calculation of the date of delivery may be slightly different for women who carry out accurate and conscientious observations of changes occurring in their body, including physical characteristics of mucus and body temperature. It is then possible to take as a starting point the day of probable ovulation and fertilization. Unfortunately, from experience I know that not every doctor wants to take into account information that a woman gives him, because he does not believe that she actually knows what she is saying.
Calculation of pregnancy age and due date based on ultrasound examination
Ultrasound is particularly useful for women who did not have regular menstrual cycles before pregnancy and whose Naegele rule is of limited use. The most useful parameter on the basis of which ultrasound can be used to determine pregnancy age and delivery is fetal parietal length (CRL). CRL is all the more reliable the earlier it was measured (optimally by the 10th week of pregnancy).
As the pregnancy progresses and the fetus grows, CRL becomes impossible to determine. In such a situation, measurements such as the two-scale fetal head size (BPD), femur length (FL) and transverse fetal cerebellar dimension (TCD) can be used.
When to speed up due date
As we know very well, life writes different scenarios, and the moment of delivery does not always coincide with the calculations. According to statistics, only 4 women out of 100 give birth in a given time. Many children are born on a different date, which differs from the proper one by about 2 weeks.
A normal pregnancy lasts from 38 to 42 weeks. However, the fetus does not always grow at the same rate.