Your Due Date

The day your baby is due is called the estimated date of delivery (EDD). Although only approximately 1 in 20 women give birth on their EDD, it is useful because it serves as a guide for your baby’s growth, your pregnancy’s progress and the timing of prenatal tests. In some cases, the test result depends on the stage of your pregnancy.

Some women know the exact date their baby was conceived — either by ovulation symptoms or by using an ovulation prediction kit. But most women do not know this date. For this reason, the “menstrual dating method,” which is based on the first day of your last menstrual period, is used to calculate the EDD.

To calculate your estimated due date:

  • Take the date that your last normal menstrual period started.
  • Add 7 days.
  • Count back 3 months.

Example: The first day of your last menstrual period was January 1. Add 7 days to get January 8. Then count back 3 months. Your due date is October 8.

You may notice that your last menstrual period is included in this dating method, even though your baby wasn’t conceived yet. Pregnancy is assumed to occur 2 weeks after your menstrual period, so an extra 2 weeks is counted at the beginning of your pregnancy when you aren’t actually pregnant.

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