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

If a couple of trying for a baby and having sex every day, they can’t know which day was successful, so you go off a day you know for sure. That gives doctors a rough estimate of how far along the mother is, until they can do other tests to get a more accurate picture, such as ultrasounds.

Between the known date of their last period and visual evidence of the fetuses development, they can then make a pretty accurate guess on how far along the pregnancy is and when they expect the due date to be.