Due Date (Pregnancy)
The estimated date of delivery, calculated as 280 days (40 weeks) from the first day of the last menstrual period.
Naegele Rule: LMP + 280 days = estimated due date. Only 5% of babies arrive on their exact due date. About 80% arrive within 2 weeks (38-42 weeks). First pregnancies average 41 weeks and 1 day. The most accurate dating comes from an early ultrasound (6-12 weeks), which measures the embryo directly rather than estimating from cycle dates.
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