Skip to content

40 Week Countdown


I like numbers. I like 6 the best because it’s a perfect number.

1 + 2 + 3 = 6
1 x 2 x 3 = 6

Amazing! What is not amazing is the published statistic that pregnancy is a 40 week condition. It is not amazing in two ways:

  • Technically it’s incorrect.
  • Who wants to be generally uncomfortable for 40 weeks?

So good news, there is a difference between what doctors call the “gestational age” and how many weeks you actually have a little being growing inside of you. Gestational age starts on the first day of your last period. ( For those of you out there that can apply basic logic, that would mean that you could NOT, in fact, be pregnant on that day because you had your period and the two are mutually exclusive. So why start counting then? Well because most women do not know the exact day they became pregnant – though you might be able to wager a pretty good guess if you have been charting your temperatures. So the assumption is that you ovulated 16 days after the first day of your last period and thus got pregnant on that day. The problem with this approach is that all women are different (as any man will tell you!). What is true for one of us is not for others. So in terms of actual growing time, the baby is actually two-ish weeks “younger” than it is credited by your doctor and the ultrasound. Make sense? No? Join the club, but I hope at least that explanation made the number of weeks shown on the ultrasound sheet a little more helpful. This is also helpful to know if you are calculating your own due date prior to seeing your doctor.

Due Date = First day of last period + 40 weeks


Due Date = Day of Conception + 38 weeks

Voila. Pregnancy Math 101.

Now when do I get to that second trimester? Well that is really not a calculation, but a matter of opinion it seems. My doctor claims it’s 12 weeks (meaning baby has been growing for 10 weeks). Other sources say 13 weeks to put you at 11 weeks of baby growth. ( It does not appear to matter much past curiosity because your morning sickness is going to go away when it darn well feels like it, not when you hit a magical time marker.

Now about this “morning” sickness….

One Comment leave one →
  1. Carleigh permalink
    05/12/2011 18:26

    All the numbers are really just a joke. Baby #1 came at 39 weeks. Baby #2 had to be evicted (induced) at 41 weeks. Who knows what is really going on and how long it’s really supposed to last. I read that the “40” week number is a really old statistic and doesn’t mean much to our modern day pregnancies anyway. Isn’t it something like on 4% of babies arrive on their due date?

    Anyway, big congrats to you guys! So happy for you. 🙂

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: