Since the "full gestation period" is 40 weeks, and separated into 3 sections/trimesters, a lot of people divide 40 by 3, coming up with 13.333... concluding that each trimester is roughly 13.3 weeks (roughly). So, the beginning of your 2nd trimester is 13.3 weeks, the beginning of your 3rd trimester is 26.7 weeks, and full gestation is at 40 weeks.
So, I guess the beginning of the 3rd trimester is somewhere around 26 weeks and 5 or 6-ish days? Maybe?
Re: ?
Since the "full gestation period" is 40 weeks, and separated into 3 sections/trimesters, a lot of people divide 40 by 3, coming up with 13.333... concluding that each trimester is roughly 13.3 weeks (roughly). So, the beginning of your 2nd trimester is 13.3 weeks, the beginning of your 3rd trimester is 26.7 weeks, and full gestation is at 40 weeks.
So, I guess the beginning of the 3rd trimester is somewhere around 26 weeks and 5 or 6-ish days? Maybe?
Anyway... Math!