trimester breakdown

there is alot of confusion about how long pregnancy actually last. The old tale is that it should be 9 months, but ask any Dr. and he/she will tell you 10 months.Why the month difference?
The period from conception to birth. After the egg is fertilized by a sperm and then implanted in the lining of the uterus, it develops into the placenta and embryo, and later into a fetus. Pregnancy usually lasts 40 weeks, beginning from the first day of the woman's last menstrual period, and is divided into three trimesters, each lasting three months.
A normal pregnancy is 10 lunar months and 9 calendar months. Midwives and doctors speak of pregnancy lasting 40 weeks- they do not use "months" at all. So get used to thinking of pregnancy as 40 weeks and nothing to do with months.

Trimester Breakdown

First trimester:

Month 1 — week 1 to 4
Month 2 — week 5 to 8
Month 3 — week 9 to 13

Second trimester:

Month 4 — week 14 t0 17
Month 5 — week 18 to 21
Month 6 — week 22 to 26

Third trimester:

Month 7 — week 27 to 30
Month 8 — week 31 to 35
Month 9 — week 36 to 40