As soon as a woman finds out she is pregnant, one of the first things she wants to know is when she is due. Knowing this date is particularly important in our society, where women often need to schedule a maternity leave far in advance of the birth. Knowing a baby's due date can also give parents a time frame in which to prepare for the baby's arrival. There are several ways of calculating a due date, but two methods are most commonly used by obstetricians.
Step 1
Determine the first day of your last period.
Step 2
Add 40 weeks, or 280 days, to the first day of your last period. The date you end on will be your due date. Since doctors cannot determine the exact date of conception, they assume you conceived around 2 weeks after the first day of your last period--this is when most women ovulate.
Step 3
Add 38 weeks from the date of conception. This is an alternate method that should only be used if you know the exact date of conception.
Step 4
Make an appointment with your obstetrician and schedule an ultrasound. Measurements taken of your baby during an ultrasound can provide a very accurate gestational age, which can help calculate your due date.
Tips and Warnings
- According to the American Congress of Obstetricians and Gynecologists, only 5 percent of women actually give birth on their due dates. Therefore, flexibility and an open mind are important when waiting for the arrival of a baby.
- Prenatal care is essential to the health of pregnant mothers and unborn babies. Even though it is possible to calculate your due date at home, you should still contact your OB/GYN or family practitioner as soon as you become pregnant.
Things You'll Need
- Calculator (optional)
