There are several ways to know the approximate day your baby will be born.
By Mayra Martínez
It is always taken into account that a pregnancy consists of nine months, although gynecologists count 40 weeks from the first day of the last period. So how long does the pregnancy last?
MONTHLY MONTHS
Pregnancy lasts 10 lunar months of four weeks each. That is, 40 weeks from the first day of the last menstruation. However, identifying that date or the exact day on which we conceive our child is not always so easy. Firstly, because we do not usually record our first day of the period and we do not usually record when we had sex.
NAEGELE RULE
This German gynecologist adjusted the duration of the pregnancy to 280 days, that is, 40 weeks or 10 months. Naegele based her calculations counting from the first day of a woman’s last menstrual cycle. However, since conception does not occur until two weeks later (in regular women), it actually takes 38 weeks for a baby to develop or 266 days.
MEDICAL CALCULATION
When you visit your gynecologist for the first time he asks you when was the first day of your last period. Taking that date as a reference, it uses an instrument formed by two overlapping cardboard wheels that rotate, one placed on that day and the other that counts the number of weeks from that date until reaching 40. However, if your rules are irregular, the calculated date may fail. For this reason, the possible date of delivery is checked again on the first routine ultrasound in week 12 of pregnancy. During the control, the length between the head and the sacral bone of the fetus is measured and related to the reference values.
Most pregnancies last from 37 to 42 weeks, but some take longer. If your pregnancy lasts more than 42 it is called prolonged or post-term. Many doctors already take week 41 as an indicator to schedule a delivery due to the risk that the probable date was miscalculated and they put both your health and the baby’s health at risk.