When does 2nd trimester officially start?

Is it at 13 or 14 weeks? I have read both answers online. TIA!

Re: When does 2nd trimester officially start?

both everyone tells you differently.

i decided that when i was 13 weeks 1 day, i was officially in my second tri. it's a personal decision, really, since no one will give us a straight answer!!

Re: When does 2nd trimester officially start?

I've always seen 14 weeks. My pregnancy journal said 14 and so did the Baby Center email and What to Expect book.

I also had a weird allergic reaction at 12 1/2 weeks and when I was at the hospital they said they couldn't give me one of the mediactions while still in my first trimester and they said I had another 1.5 weeks before the second, which would be 14 weeks.

This link shows the American Pregnancy Associations list of weeks and they have Week 14 starting your 2nd trimester:

American Pregnancy Assn

Re: When does 2nd trimester officially start?

I am going with 14 wks........most of the books I have said that is when it begins.

Re: When does 2nd trimester officially start?

Depends on who you speak to/read.

Online it says 13 or 14 weeks, but on my Dr's website it says 12 weeks. Also, my doctor said at my 12 week appointment, "Welcome to the 2nd Trimester"

I don't think anyone really knows

Re: When does 2nd trimester officially start?

funny you bring this up... I'm also on the cusp of the end of the first trimester....

I got annoyed with all the conflicting info, so I thought about it logically...

pregnancy lasts 40 weeks from the last period.... so, let's divide it into three chunks...

13.3 weeks per trimester! Since it's 13 + change, by 14 weeks, it's definitely 2nd trimester turf

so, for me, I'll turn 14 weeks on sunday....