What trimester am I in?!

[LittleMissPear]

I am 13 weeks today, I have three different apps on my phone, all of which say different things. One says today is the first day of the 2nd trimester, the other says 14 weeks and the other says 15! Can anyone shed any light?

[eurochick]

Well if you divide 40 by 3, you get 13.3333 so I considered that I was in the second tri at 13+4. But definitions differ as you have discovered!

[PenguinsEatSpinach]

Most people would say that the second trimester starts at 14 weeks I think. Because three months is 13 weeks, so you need to do 13 full weeks to be three months' pregnant.

[iwantittobepink]

I'm 13 weeks today too, so according to my pregnancy journal it's the second trimester! X

[squizita]

My midwife said as you start at week 0 (1st week), 13+ is 'into' week 14 (if that makes sense) and thus 2nd!