Obstetrics - Prenatal care

 

Due date

The day your baby is due is called the "estimated date of delivery," or EDD (also known as estimated date of confinement or EDC). A typical pregnancy lasts 40 weeks from the first day of your last menstrual period. Although only about 1 in 20 women deliver on their exact due date, the EDD is useful for many reasons. It is used as a guide for checking the baby's growth and the progress of your pregnancy. Your due date also affects the timing of prenatal tests. In some cases, the test results depend on the stage of pregnancy.

 

There are a number of ways to figure your due date. They often are used together to help predict when your baby will be born. Most women go into labor within 2 weeks of their due dates—either before or after. To get an idea of your due date:

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

 

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

 

This technique is based on a 28-day cycle, with conception occurring 2 weeks afterward. This presumption does not apply to all women.

 

Having an ultrasound exam, if needed, in the first or second trimester can help to confirm your due date. If the ultrasound due date is very different from your menstrual due date, your obstetrician or midwife may change the due date.

 

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