Dating a pregnancy

[studentvera]

Stupid question I know but does your pregnancy start as day one the day you conceive/ovulate or does it start of date of last period so it's 2 weeks old when you dtd!

Obviously you can't biologically be pregnant before you ovulate! So the pregnancy starts at conception, which happens on the day you ovulate.

However, most women do not know exactly when they ovulate. So the doctors and midwives use a counting system from your last period. Because most women can tell you when abouts their last period was, especially if they are ttc.

So most people, when they miss their period, are "4 weeks pregnant". The embryo has only been alive for 2 weeks though. But the extra 2 weeks when there was no baby are included in the counting system that has 40 weeks of pregnancy.

With dating scans these days, the old system is a bit out of date. But once upon a time, a woman's last period was the only date midwives had to go on.

Yup, you count 40 weeks from the day of your last period. That will be your estimated due date. May get changed a few days either way at your 12 week scan.

Thank you for replies.

So is 12 week scan - 12 weeks after last period? So 10 wks after ovulating?

Sorry for all the questions!

Yes! :)