naegele's rule is a standard way of calculating the due date for a pregnancy. the rule estimates the expected date of delivery (edd) by adding one year, subtracting three months, and adding seven days to the first day of a woman's last menstrual period (lmp). the result is approximately 280 days (40 weeks) from the lmp. ==history== naegele's rule is named after franz karl naegele (1778â1851), the german obstetrician who devised the rule. naegele was born july 12, 1778, in dÃ¼sseldorf, germany. in 1806, naegele became ordinary professor and director of the lying-in hospital in heidelberg. his lehrbuch der geburtshilfe, published in 1830 for midwives, enjoyed a successful 14 editions. ==calculation== the rule estimates the expected date of delivery (edd) (also called edc, for estimated date of confinement) from the first day of the woman's last menstrual period (lmp) by adding one year, subtracting three months, and adding seven days to that date. the result is approximately 280 days (40 weeks) from the lmp. example: lmp = 8 may 2009 :+1 year = 8 may 2010 :â3 months = 8 february 2010 :+7 days = 15 february 2010 280 days past lmp is found by checking the day of the week of the lmp and adjusting the calculated date to land on the same day of the week. using the example above, 8 may 2009 is a friday. the calculated date (15 february) is a monday; adjusting to the closest friday produces 12 february, which is exactly 280 days past 8 may. the calculation method does not always result in 280 days because not all calendar months are the same length; it does not account for leap years. parikh's formula is a calculation method that considers cycle duration. naegele's rule assumes an average cycle length of 28 days, which is not true for everyone. edd is calculated using parikh's formula by adding nine months to lmp, subtracting 21 days, then adding duration of previous cycles. in modern practice, calculators, reference cards, or sliding wheel calculators are used to add 280 days to the lmp. ==accuracy== the lmp may not be the best date to use as the basis of a due date calculation, but it remains popular because few women know exactly on which day they ovulated or conceived a pregnancy, and because no algorithm can predict the exact day that spontaneous labor will occur no matter what considerations are taken into account. ===average gestation of 40 weeks=== naegele's rule presents 280 days after lmp as an estimate for the average onset of spontaneous labor. a number of studies have been published in recent years to support continued use of this number: [[image:sta
Equations Human_pregnancy Medical_ultrasonography Obstetrics Rules_of_thumb