How is the Estimated Date of Delivery (EDD) calculated using Naegele's Rule?

Naegele's Rule is a standard way of calculating the Estimated Date of Delivery (EDD) for a pregnant person, typically based on the first day of their last menstrual period (LMP). To apply Naegele's Rule, you start with the date of the LMP. The calculation involves a straightforward adjustment of the date that accounts for the typical 28-day menstrual cycle and the 40-week duration of a pregnancy.

To compute the EDD using Naegele’s Rule, the following steps are taken: you take the LMP date, subtract 3 months (to account for the fact that pregnancy is calculated from the first day of the last menstrual period), then add 7 days to reach the estimated delivery date. Finally, since pregnancies usually cross over into a new year, you may need to adjust the year by adding one. This method effectively shifts the conception date forward to align with the standard prenatal timeline.

Choosing to subtract 3 months, add 7 days, and then add 1 year when necessary captures the essence of the calculation method that Naegele outlined, making it a reliable way to estimate when a person is likely to give birth. This process is significant in prenatal care and planning, as it helps both patients