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Calculating Your Baby's Due Date - Pregnancy Planner

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The “estimated date of delivery” (EDD), or “due date” as it is commonly called, is the expected date that you will begin labor. As the name suggests, this date is just an estimate. It is likely you will start labor any time from two weeks before or two weeks after this estimated date. It is unlikely that your baby will be born exactly on the estimated date of delivery. In fact, only 5% of babies are born on the exact due date.

There are a few different ways to estimate your due date:

  • The most accurate way to determine your estimated due date is by using your date of ovulation to find the age of the fetus. However, the exact date of your ovulation is rarely known.
  • The most common way to determine your due date is by using your menstrual calendar. This method is not exact because it is effected by the regularity of menstruation, which changes from month to month and woman to woman. It is also sometimes hard to remember exactly when your last period was. In this case, keeping a menstrual calendar is helpful. Despite not being 100% accurate, it is the easiest way to get a useful prediction. To calculate your estimated due date using this method take the first day of your last menstrual period, add seven days to that, and count back three months. For example, if your last menstrual period started on May 2nd, add 7 days to get May 9th and count back three months to get March 9th. This means that you can expect your baby to arrive around March 9th.
  • Your doctor can tell how far along in your pregnancy you are by listening to the baby’s heartbeat using a special ultrasound device. In most pregnancies, the fetal heartbeat cannot be heard until about 10 to 12 weeks.
  • Your doctor can also use an ultrasound device to convert sound waves into a picture that you can see. He or she can use this picture to set the age of the fetus within about a week. This method is used during the first half of the pregnancy. As the pregnancy progresses past the first half, accuracy of the method declines.

Whichever method you use to determine your expected due date, it is an important and necessary step. The months ahead of you are full of planning and learning so that you are prepared for the arrival of your new baby.

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