How is a woman's due date calculated?

Question

Quizplus · Accepted Answer

Pregnancy typically lasts about 266 days from conception, or about 280 days from a woman's last menstrual period. If she knows the date she conceived, she can more accurately calculate her due date. If she is not sure when her last period was, or if she had some early spotting that she thought was a light period, the due date could be miscalculated. In these cases, a healthcare provider may order an ultrasound to confirm the due date. The number of days works out to be 40 weeks or about nine months. A baby can safely be born between 37 and 42 weeks gestation, so a pregnant mom might better think of it as a due month than a due date!

How Is a Woman's Due Date Calculated