How accurate is my pregnancy due date?
Due dates are estimates, not guarantees. Only about 5% of babies are born on their exact due date. Most babies arrive within 2 weeks before or after the estimated date, which is completely normal. See also our Period Calculator.
How is my due date calculated?
Due dates are calculated by adding 280 days (40 weeks) to the first day of your last menstrual period. This assumes a 28-day cycle and ovulation on day 14. The calculation may be adjusted for different cycle lengths or other factors.
Can my due date change during pregnancy?
Yes, your due date may be revised based on ultrasound measurements, especially early ultrasounds which are very accurate for dating. Your healthcare provider may adjust the date if there's a significant difference between the calculated and ultrasound dates.
What if I don't know my last menstrual period date?
If you don't remember your last period, you can use the conception date if known, or rely on early ultrasound dating. An ultrasound performed between 8-13 weeks is most accurate for determining gestational age. You might also find our Estimated Due Date — Pregnancy useful.
How soon can I take a pregnancy test?
Most home pregnancy tests can detect pregnancy as early as the first day of a missed period. For the most accurate results, wait until at least one week after your missed period or consult with your healthcare provider.
What's the difference between gestational age and fetal age?
Gestational age is calculated from the first day of your last menstrual period, while fetal age (conceptional age) is calculated from the actual conception date. Gestational age is typically about 2 weeks longer than fetal age.
How likely am I to give birth on my due date?
Very unlikely! Studies show that only about 5% of babies are born on their exact due date. About 85% of babies are born within two weeks before or after the due date, which is considered full-term. Check out our Due Date Calculator as well.