How to compute pregnancy age?

Question

My periods are usually irregular so im not sure how doctors count the weeks. Gynac told me im 7 weeks but i dont understand how she got that. Can someone explain how this is calculated from?

Zenia Kamath · Answer

Oh i was confused by this too, i thought it counts from when you conceive. So its from the last period? Thanks, that clears my doubt.

Madhuri Phadke · Answer

My doc counts it from the first day of your last period, not from conception, so it sounds about 2 weeks more than you expect. The early dating scan then confirms it. Thats why due dates are 40 weeks from that first day.

Damini Garg · Answer

Count from first day of last period. Scan confirms it.

Geeta Bajaj · Answer

I just put my last period date into a pregnancy app and it gave the weeks and due date instantly. Super handy. The first scan later matched it pretty closely.