It’s important to know when your baby is due, and not just so you can plan your work leave (and baby shower) in advance. If a pregnancy goes too far past the due date, medical intervention such as induced labour or a cesarean section may be necessary.

Calculating the due date is not as exact as it may seem. The rule of thumb is that pregnancy lasts 38 weeks (266 days) from the date of conception, and the date of conception is normally assumed as 14 days after the start of the woman’s last period. But it must be remembered that this is only an approximation. Conception is not always on the fourteenth day after the start of the period. And the pregnancy itself may last a week or more longer; especially if it is your first pregnancy, or your periods are irregular or more than 28 days apart.

That said, the 266-day pregnancy is still useful as a base measure for planning. We’re also giving you the start dates for your second and third trimester - the standard landmarks for pregnancy. The first trimester is the time associated with morning sickness and hormone shifts. These difficulties tend to disappear by the second trimester, which is usually when the pregnancy starts to show. As of the third trimester, the baby will be quite large, and the mother will tire more easily. In the third trimester, the baby will most likely be able to survive if born prematurely.

Baby due date calculator

Enter the first day of your last period (i.e., when menstruation began):