Determining your due date

You can calculate your own due date, or your doctor or midwife will do it for you at your first prenatal care visit. Your due date is an estimate and will be approximately 40 weeks from the first day of your last menstrual period.

Even though your baby is not conceived until about two weeks after you start your period, week one of your pregnancy is considered to be the week of your menstrual period.

Your first trimester lasts until the end of week 13, the second trimester lasts from week 14 to the end of week 26, and your third trimester is from week 27 until birth. Most babies are born between weeks 38 and 42.