Why do pregnancies start counting from the last day of your period instead of the day of conception?

Question

Also, how accurate is the due date?

In: 801

Answer 1

I’d wager it’s because it was the most accessible way. Women will always have been aware of their cycle, and without modern tools such as ultrasound or blood testing its a useful data point. Yes there will be variables but an average cycle is 28 days.

Then once the pregnancy is older you can use things like fetal heart rate and size on palpation to confirm.

The due date takes this into account