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

Regarding the accuracy part, you need to clarify what you mean by that. Is it the median date (50% probability they baby is born on that day or later, 50% earlier)? Yes, quite accurately.

But the probability that the baby is born on that day is only 4%. And it goes down on the other days (before and after) like a Gaussian (truncated because at some point we take them out).