i am abit confused about how they know how far gone you are! for example if i go for my scan and they say i am 8 weeks does that mean i had sex 8weeks ago and got pregnant on that day?
The way pregnancy is dated is, the first day of your very last period, is the first day of pregnancy, however, actual conception takes place around 2 weeks later.
This means your pregnancy is classified as 8 weeks, but the actual age of your Embryo is only about 6 weeks.
The entire term of pregnancy is 40 weeks, although when babies are born, they are generally around 38 weeks old, if on time that is.
the date is always taken from the first day of last period. Once a dating scan takes placeat about 12 weeks the date may be changed IF it varies by 7 days or more from the LMP date (last menstrual period)
because its taken from the first date of you last period there is a possible 4 week discrepancy, so although your classed as 40 weeks full term some hospitals wont induce a late baby until 42 weeks.