What week is the second trimester???

Looking on the internet I am getting mixed answers...most say 13 weeks, and some say 14 weeks. I know I could call my doc, but I thought I would ask the pros (you ladies)!!

If its 13 weeks then I will already be in my second trimester next week! WOW!!  :)

Alot of books say 12 or 13. My OB says 13. Yah your almost there!!
Jessica

14

 It was confusing for me too, but if you divide 40weeks by 3trimesters... you get 13.3 weeks. So right there is the sweet spot lol

My OB goes by 13 weeks.

I use Days Of Pregnancy on www.pregnology.com It is awesome for this sort of thing.

I'm going with 13 weeks. Looks like we'll hit it the same day. Only 1 more week! I go for my NT scan this morning and I measured a little further ahead at my first U/S, so I'm hoping they might tell me I'm measuring 13 weeks.