Nine or Ten Months?

I have been writing about the Presidential race for a while now, so how about if we mix it up a bit?

When I was at a party this weekend, I ended up in a disagreement with a pregnant woman. It is an old argument I have had with several women over the years: Is a woman who gives birth to a baby on her due date pregnant for nine months or ten?

The general rule is that gestation lasts for 40 weeks. Women who think gestation lasts for ten months are assuming that the average month has four weeks. This is fine if you are using a lunar calendar, but the calendar on my wall is Gregorian. The average Gregorian month has about 30.5 days, which is about 4 1/3 weeks. If you count 9 of these months, you get 39 weeks. That means that 40 weeks is nine months and one week.

But wait! The clock starts ticking for the 40 weeks on the first day of a woman's lunar cycle (if you get my drift.) This means that for several days of the time counted in the duration of the pregnancy, it is quite impossible for the woman to be pregnant. Ovulation doesn't generally happen until at least day 10, so we have really lost that extra week and some change.

Here is Babies Online's response to this question.

Let me be completely clear: However long it lasts, pregnancy is not for the weaker gender (that's us guys.) If men had to go through it, our species would have died out eons ago. Pregnancy and the first months following pregnancy are way too tough for any guy to handle it. I just don't buy the argument that pregnancy lasts 10 calendar months. It's 9 months that no man could ever relate to.

Sorry to go all biology-geek on you, but I wanted to get that off my chest. Now that I have, I no longer need to argue with a pregnant woman about this. I can pass the URL for this post to her significant other and leave it at that.