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Pregnancy Due Date Calculation:
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The pregnancy due date calculation estimates the expected delivery date based on the first day of the last menstrual period (LMP). This is commonly known as Naegele's rule, which adds 280 days (40 weeks) to the LMP.
The calculator uses the standard obstetric calculation:
Where:
Explanation: This calculation assumes a regular 28-day menstrual cycle with ovulation occurring on day 14. The calculator also shows current gestational age based on today's date.
Details: Accurate due date estimation is crucial for proper prenatal care, monitoring fetal development, and planning for delivery. It helps identify preterm or post-term pregnancies that may need special attention.
Tips: Enter the first day of your last menstrual period (LMP) in the date field. The calculator will show your estimated due date and current gestational age.
Q1: How accurate is this due date calculation?
A: Only about 5% of women deliver on their exact due date. Most deliver within 2 weeks before or after the estimated date.
Q2: What if my cycles aren't 28 days?
A: The calculation may need adjustment. For longer cycles, add the extra days to the due date. Your healthcare provider can make this adjustment.
Q3: How is this different from ultrasound dating?
A: Early ultrasound (especially first trimester) may provide a more accurate estimate, particularly if menstrual dates are uncertain or cycles are irregular.
Q4: Why 280 days if pregnancy is 9 months?
A: Pregnancy is actually about 9.5 lunar months (4 weeks each). 280 days accounts for 40 weeks from LMP (which includes about 2 weeks before conception).
Q5: When should I contact my doctor about the due date?
A: If you're uncertain about your LMP, have irregular cycles, or if your ultrasound due date differs significantly from LMP-based calculation.