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

It all comes down to reliable information.

If you find an OBGYN who regularly works with moms who practice Natural Family Planning (NFP) and keep good logs. (or something similar) Those Dr’s offices often use conception date instead of, or in conjunction with, the date of the last period.

A good amount of couples don’t know exactly when they are fertile, so the last period is a more reliable data point for many people, and it’s close enough to accurate to provide good healthcare based on that data alone.

TLDNR: Conception day is more accurate but harder to know and the last period date is good enough.