Pregnancy Due Date

Pregnancy, Trimesters and Fetal Development
Pregnant woman silhouette on black

The little stick shows two pink lines? Congratulations, you are pregnant! After you conduct your home pregnancy test, you anxiously make an appointment to see your doctor. You most likely will have several questions, but the most common one is, “When am I due?”

Pregnancy due date basics. Your pregnancy due date tells you when your baby will be arriving, approximately. It is estimated only about 4 percent or 5 percent of babies actually are born on their calculated due dates. The medical term for the due date is the estimated date of confinement, or EDC.

Calculating your pregnancy due date. To calculate your pregnancy due date, determine the first day of your last menstrual period. When you know what the date of your last menstrual period was, count ahead 40 weeks from that date. The date that you arrive at is your pregnancy due date. Using this method, the typical pregnancy lasts about 280 days, based on an average 28-day menstrual cycle. According to the American Pregnancy Association, due dates are based on the first day of your menstrual period because the exact date of conception is almost never known.

Due date calculators. Several due date calculators are available online. The Mayo Clinic, and each have calculators. Simply enter the date of your last menstrual period into the calculator and click. Your due date will be calculated for you.

Determining due date with an ultrasound. While you can use the date of your last menstrual period to determine your due date as soon as you know you are pregnant, an ultrasound may be used later. Ultrasounds may be performed as early as five weeks after your last menstrual period. However, typically it is done between the eighth and 18th weeks. The ultrasound will measure the development of the baby. If you have irregular periods, an ultrasound may help in determining your most accurate due date.

This article was originally published as Pregnancy Due Date on

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