When is your baby due? Eh… Give or take a few weeks.

I just read a fantastic news article that explained what many midwives have been proclaiming all along. A pregnancy does not last a set amount of time. In fact, it can vary up up to five weeks!

Previously attributed to flawed methods of estimating due dates such as conception and implantation dates varying and poor maternal recollection, scientists have discovered, that human pregnancies generally last between 37 and 42 weeks for an entirely different reason as well.

So, how many women deliver on the 280th day after the start of their last menstrual period? Only about 4%.

Big deal, right? People ovulate at different times. Yada yada.

Researchers from the National Institute of Environmental Health Sciences (NIEHS) across the pond were able to pinpoint exactly when women became pregnant by taking daily urine samples. And then they began the countdown to labor. They published their work earlier this month in the journal Human Reproduction.

The average duration from ovulation to birth was 268 days. So, on average, after ovulation (which happens around two weeks after the first day of a woman’s period), the baby wouldn’t arrive for another 38 weeks and two days. The big finding though was remarkable, because this method of counting doesn’t include any of the variables that normally are blamed on the cause of inaccurate prediction of a baby’s arrival. The big finding was that even STILL, healthy babies arrivals varied by up to 37 days, even in this small test group.


Read also: The Due Date Debacle

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