How to Figure Pregnancy Due Date
Learning that you have a baby on the way is a life-changing moment. You will want to know when your baby will arrive, and to do so takes a few simple steps. While the majority of babies born aren't born on their due date, knowing your due date can be helpful in knowing an approximate time frame for when you will give birth.
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Instructions
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Addition Method
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1
Mark on your calendar the first day of your last period. If you can't remember the exact start date, then mark as closely to the beginning of your last period as you can remember.
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2
Count forward from that date by 40 weeks or 280 days. The date you reach by this count is approximately your due date.
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3
Check your calendar to see which date it was that you began ovulating, if you kept track of that. From that date, count ahead 38 weeks, or 266 days. The date that you wind up on is your due date.
Subtraction Method
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4
Make note of the first date of your last period on your calendar. Add seven days to this date.
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5
Count backward three months, or 12 weeks, from the date you got in the first step. The date you wind up on once you count backward is your due date.
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6
Check your ovulation date on the calendar, if you know it. Count backward three months from this date and you will wind up at your due date.
Online Calculation
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7
Visit an automated pregnancy calculation website such as site provided in the Resource section below.
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8
Enter the first date of your last period. Check your calendar if you cannot remember offhand.
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Enter the average length of your menstrual cycles, then hit enter and the website will calculate your due date for you automatically.
Seeing a Doctor
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10
Make an appointment with your obstetrician to receive an ultrasound. The sooner you schedule your ultrasound, the better. Ultrasounds to calculate due dates are more accurate the earlier in your pregnancy you are.
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11
Have your obstetrician give you a transvaginal ultrasound if you are within your first five weeks of pregnancy. From this your doctor can tell you your due date within a five-day range of accuracy.
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Have your obstetrician perform a regular ultrasound if you are further along than five weeks. Your doctor will be able to tell you your due date withing a 10- to 15-day range with this method.
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Tips & Warnings
In order to know your due date, it is important to have kept track of your period schedules before becoming pregnant. Keeping a calendar of your period is recommended if you are trying to get pregnant. These methods of calculation are based on a cycle that averages 28 days. If you know the length of your cycle, you will need to adjust the counting accordingly to match your personal menstrual cycle length.
