So, Due Dates Probably Aren't Even A Thing



Pregnancy is 40 weeks long. Everyone knows that.

Except we’re finding out that maybe it isn’t 40 weeks. It might only be 38 weeks. Or 43 weeks. Or maybe 42 weeks. You see, new research has found out out that length of pregnancy varies and due dates are LIES, ALL LIES.

Ahem. I may still be upset about how my first baby was due at the end of 2007 but wasn’t born until 2008. Seems like doctors should be able to get the year right, huh? Yeah, no. No.

Anyway, researchers at the National Institute of Environmental Health Sciences (NIEHS) in England are trying to get a handle on how long pregnancy actually lasts. We’ve always knows it was somewhere around 38-42 weeks, but the discrepancies were assumed to be because of imperfect dating at the start of pregnancy. The standard means of calculating when a pregnancy would culminate was to add 280 days to the date of the pregnant person’s last menstrual period.

In this study, researchers conducted daily urine tests on 125 people to pinpoint the exact day pregnancy began. What they discovered was that the average length of gestation among their cohort was 268 days — or 38 weeks and two days. But — and this is a big but — length of pregnancy could vary from that by as much as 37 days.

So my 290-day first pregnancy was totally normal and not anything I should have worried about. It was just annoying to be pregnant that much longer than I wanted to be.

Whether this research will begin a sea change in how we regard the idea of “past dates” or “early labor” remains to be seen. What we can say for sure is that pregnancy, like pretty much every other human condition, isn’t one-length-fits-all.

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