[Sonny M]

40 weeks is the normal gestation period.

Your using Naegele's Rule I am assuming.

That said, I've rarely ever met an expectent mother who claimed to be more then 9 months pregnant and no one refers to a mother who gives birth to a child at 9 months "premature".

[elc]

Most people still say 9 months. And yes the 10 month rule is based on LMP. But most expectant mothers, including myself, that I've talked to or met on forums knows that its actually 10 months long. You're not even considered late until you are 42 weeks.

[wideawake]

The gestation period is 40 weeks or 280 days (which usually includes at least a couple of extra days since it's counted from the last date of menstruation and not the day of conception). The average month is 30.4 days long.

280 days divided by 30.4 is 9.2 months or 9 months and 6 days.

So both 40 weeks and 9 months are correct, give or take a few days.