Due Date Calculator
The Due Date Calculator estimates the delivery date of a pregnant woman based on her last menstrual period (LMP), ultrasound, conception date, or IVF transfer date.
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About Due Date Calculation
Naegele's Rule: The most common method for calculating due dates is Naegele's rule, which adds 280 days (40 weeks) to the first day of your last menstrual period (LMP). This assumes a 28-day menstrual cycle with ovulation occurring on day 14.
Ultrasound Dating: Early ultrasounds (before 20 weeks) are the most accurate for dating pregnancy. The ultrasound measures the baby's size and compares it to standard growth charts to estimate gestational age.
IVF Pregnancy: For IVF pregnancies, the calculation is based on the embryo age at transfer. A day 3 embryo transfer is equivalent to 17 days after LMP, while a day 5 transfer is equivalent to 19 days after LMP.
Understanding Due Dates
Accuracy of Due Dates
Only about 5% of babies are born on their exact due date. Most babies are born within 2 weeks before or after the estimated due date. A pregnancy is considered full-term between 37 and 42 weeks.
Factors Affecting Due Date
Several factors can affect the accuracy of due date calculations, including irregular menstrual cycles, the timing of ovulation, and individual variations in pregnancy length. Your healthcare provider may adjust your due date based on ultrasound measurements.
When to Contact Your Healthcare Provider
Contact your healthcare provider if you go past your due date, experience any concerning symptoms, or have questions about your pregnancy timeline. Regular prenatal care is essential for monitoring your pregnancy progress.