Why do we calculate the length of a pregnancy from the first day of a women’s last period?
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On average, a woman’s body works on a 28 day cycle. That means that she usually ovulates on day 14, or about halfway through.
Ovulation is when the ovum, or egg, is released from the ovary, a little organ that keeps the eggs, kind of like a bag. A woman has two of these little bags, and they generally take turns spitting out eggs.
The first day of the period is day 1, which is when the uterus, or where the baby is kept, cleans itself out to get ready for a new baby. It builds a cushion all along the inside walls to hold the baby. Then, doctors can usually guess the egg is ready to be fertilized 14 days after that. Fertilization when one sperm from the man finds its way to the egg and manages to join with it. Then a baby begins to grow.
This means the doctor counts about 40 weeks from day 1 for accurate timing, though babies are technically not in there for those first two weeks or so. If a woman was able to feel it when she ovulates, she still wouldn’t know the moment fertilization would occur because there are loads of variables (things that can affect it) to consider.
People say a baby grows for 9 months, but 40 weeks sounds more like 10 months, when in reality it’s about 9.5 months.
Women get an ultrasound, like an x-ray of the baby on the inside, and when the doctors measure the size of the baby they can give a more accurate date, still with an extra 2 weeks added because that’s the standard of measurement that’s used worldwide.
Babies actually come whenever they darnwell please.
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