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Naegele's rule (Nagel's rule) predicts an estimated due date based on the woman's last menstrual period. This page only provides an estimate for the due date, and does not take into account small changes such as leap years. It also does not take into affect months with less than 31 days. This page can save your due date, it is saved onto your local device with HTML 5 and is not sent to the server. The user is responsible to protect your health information. Always consult an obstetrician and obtain good prenatal care.

Due Date = LMP + 9 months + 7 days

Enter the digits for LMP, 2 digits for month and date and four digits for the year.

The official tool used by physicians to estimate gestational age from a due date confirmed by ultrasound is the Pregnancy Wheel and Ovulation Calendar.

Sources:
Books for Medical Students

1. Le, Tao, and Vikas Bhushan. First Aid for the USMLE Step 2 CK. 5th ed. New York: McGraw-Hill, 2006.

2. Naegele's rule