When does 2nd trimester start?

Question

I'm confused! Glow says that I'll be on my 2nd trimester next week (I'll be 12 weeks) But I've googled and there's other sites and stuff that says you don't start your 2nd trimester until the 14th week!!?!?!?! 
So is it the 
12th week 
Or 
14th week
2nd trimester!?!?!?
Thanks for your feedback!!!

Answer

I just hit week 13 and my app (this one) now says 2nd trimester

Answer

Mathematically, it's 13 weeks 3 days.

Answer

All depends on measurements of the baby I'm just over 12 weeks and my doctor said on my papers I'm now in second trimester 😍

Answer

Second trimester starts at the end of your 12th week so the drs said with my daughter

Answer

My dr. Says it starts at 14 wks.after that the miscarriage rate is less than 2%

When does 2nd trimester start?

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