I’m finding there’s a lot of amusing things about pregnancy I didn’t know about, but one of the more ridiculous aspects is the math. One of the first things our doctor* told us was “Did you know you’re actually pregnant for 10 months, not 9?” Not news you want to hear, particularly in the unpleasant first trimester. And, as it turns out, not entirely accurate either.
Doctors measure a baby’s age in weeks, and a typical pregnancy runs 38 weeks. “To simplify the math” as I’ve been told and read repeatedly, doctors consider the start date of the pregnancy to be two weeks before conception, on the first day of your last menstrual period (LMP), and therefore add two weeks at the end to make it a nice, even 40 weeks, “or 10 months”.
As someone who took advanced college math for fun, this drives me a little crazy. First, there’s the obvious contradiction that you’re considered pregnant for two weeks before it’s even physically possible, and second, the average month has 30.416 days in it—not 28.
A look at the [very simple, obvious] math:
Average pregnancy: 266 days (38*7)
- 9 months in doctor-months (9*28): 252 days
- 9 months by the calendar (9*30.416): 273.75 days
- 10 months in doctor-months (10*28): 280 days
- 10 months by the calendar (10*30.416): 304 days
So this is good news! Pregnancy, from conception to birth, is on average even shorter than 9 calendar months (and about 9.5 doctor-months).
The doctor-math is not without its upsides. Namely, by the time you find out you’re pregnant you’re already 4 weeks (or a “month”) along which helps psychologically: you’re two weeks closer to the blissful second trimester. And the “months” go by more quickly with milestones always falling on the same day of the week.
But for those of us who know exactly when we conceived (hat tip to Mittelschmerz), and enjoy the well-established Gregorian calendar system, taking the LMP / 40 week approach is less accurate, less logical, and causes all sorts of confusion. Here’s one good example: when we told Jeff and Molly we were pregnant in Florida, Poco and Charlie were both 10 weeks old (Poco from a gestational age, and Charlie since actual birth). Yesterday, Poco celebrated his 24 week/6-month birthday, and Charlie won’t turn 6 months until March 22nd. Initially, we thought it was fun that we would be able to gauge Poco’s age (while in utero) by Charlie’s, but obviously that’s not the case.
It just seems like time should be a consistent measurement, no?
Regardless of how you measure it, we’re having a baby in roughly 16 weeks, and that’s pretty exciting.
*It should be noted that doctor-math seems to be a universal thing and in no way specific to our doctor, whom we really like.