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# why?

why does everyone say we only have to go through 9months of pregnancy when it is really 10months? 40 weeks?

Asked by Anonymous at 9:41 AM on Oct. 29, 2009 in Pregnancy

• I'll see if this makes sense.
One month is actually not exactly 4 weeks -- it's 4 weeks (28 days) PLUS 2 or 3 days (well, except for Feburary). So then every 3 months worth of those extra 2 or 3 days add up to another week. Therefore, we say 3 months equals 13 weeks (1 trimester). That would make 9 months equal 39 weeks. So pregnancy is really more like 9 months and 1 week, so we just say 9 months.
Hope that helps!

Answer by amy_k_in_pa at 11:05 AM on Oct. 29, 2009

• because not every month has an even amount of days/weeks. so it works out to be 40 weeks but not quite 10 months. idk its weird

Answer by ashtynsmom730 at 9:45 AM on Oct. 29, 2009

• Its because pregnancy is calculated starting at your last period. Youre not "actually" pregnant at that point. When you actually conceive, youre already considered to be like 2 weeks along. So you only actually have a baby inside of you for 37ish weeks.

Answer by ma2b08 at 9:56 AM on Oct. 29, 2009

• It's actually closer to 9 months -- 9 months plus a week from your last period or 9 months minus a week from conception, generally speaking. A month is 4 weeks and 2-3 days (except February), so you have to add an extra week every 3 months (so 3 months is 13 weeks instead of 12).

Answer by DragonRiderMD at 11:01 AM on Oct. 29, 2009

• The same reason they write you BC Pill Rx for 12 packs rather than 13. They just don't think. Besides you aren't really pregnant for the first 2 weeks anyway! Then again normal is 41 weeks and 1 day and nobody can remember that. And everybody acts like if you go a day past 40 weeks you are "over due" as if your baby was a library book! If you are going to measure months use 30 days, not 28. Is isn't really 10 months. That would be 300 days. Which is almost 43 weeks.

Answer by Anonymous at 11:10 AM on Oct. 29, 2009