1st day of your last period.

[Soapie19]

Can anyone help me understand why they calculate pregnancy by the 1st day of your last period.
I'm currently 7 weeks pregnant by that calculation but surely I'm less from when I was ovulating x

I think it's something to do with not everyone will know when they ovulated and the average would dictate you would ovulate 2 weeks after first day of period if your on a 28 day cycle. I could be wrong and someone might think differently buts that's why I've always thought they do it.

@mummatara thank you that makes sense x

yep that’s why they do it and they can adjust the due date at the 12 weeks scan as they have a better idea then