Pregnancy Math

SPOILER ALERT: This post contains references to menstrual cycles.  Nothing gross though, promise.  Proceed at your own risk.

When we started talking about getting pregnant, one of the first things we considered was when the baby would arrive.  This is an important thing to know, as it creates a timeline for getting the nursery ready, planning work schedules and vacation time, budgeting, etc.

However, figuring out this ever-important date is more confusing than the movies would lead one to believe.  I had always heard two numbers related to this issue - pregnancy is 9 months long and your first trimester (when people generally start spreading the news) is 12 weeks.  Turns out, neither of these numbers are particularly helpful, or even correct.  12 weeks to a trimester would suggest a 36 week pregnancy.  False.

Side note: my doctor told me that the risk of miscarriage actually drops to almost as low as it will get once you've had an ultrasound to confirm everything looks right, which I had at 8 weeks.

Here's the magic number - 40 weeks.  Everything pregnancy-related in calculated in weeks, not months.  You may think that 40 weeks begins when the magic + sign or double lines show up on the home pregnancy test.  Not correct.  That 40 weeks actually begins from the first day of your last menstrual cycle.  But, you ask, how can this be?  If I had my period, clearly I was not pregnant yet!  And you would be right.  You are not pregnant for the first 2 weeks of the 40 weeks.

They do this because date of conception is very difficult to pinpoint (more on that in an upcoming post).  This means that for women with cycles that are significantly longer or shorter than 28 days, the due date can actually be revised based on the size of the uterus and baby as pregnancy progresses.

Confusing, right?  So when someone asks me, how far along are you?  And I say, 17 weeks, I can see that person calculating in their head how many months that is, when really what they need to know is that is almost halfway to 40 :)

February 7 is coming faster than we realize!