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Expected Due Date Formula:
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The expected due date, also known as the estimated date of delivery (EDD), is the predicted date when a pregnant woman is most likely to give birth. It is calculated based on the first day of the last menstrual period (LMP) plus 280 days (40 weeks).
The calculator uses the standard obstetric formula:
Where:
Explanation: This calculation is based on Naegele's rule, which assumes a regular 28-day menstrual cycle and ovulation occurring on day 14.
Details: Accurate due date calculation is essential for proper prenatal care, monitoring fetal development, scheduling tests, and preparing for delivery. It helps healthcare providers track pregnancy progress and identify potential complications.
Tips: Enter the first day of your last menstrual period in the date field. The calculator will automatically compute your expected due date by adding 280 days (40 weeks) to your LMP date.
Q1: How accurate is the due date calculation?
A: The calculation provides an estimate. Only about 5% of women deliver exactly on their due date, with most delivering within two weeks before or after.
Q2: What if my menstrual cycle is irregular?
A: For irregular cycles, an early ultrasound (first trimester) provides a more accurate due date estimation than LMP-based calculation.
Q3: Why is pregnancy calculated from LMP and not conception?
A: LMP is used because it's typically easier to recall than the exact conception date. This adds about two weeks to the actual fetal age.
Q4: Can the due date change during pregnancy?
A: Yes, healthcare providers may adjust the due date based on early ultrasound measurements, especially if there's a significant difference from LMP calculation.
Q5: What are the three trimesters of pregnancy?
A: First trimester: weeks 1-13, Second trimester: weeks 14-27, Third trimester: weeks 28-40+.