What method is used for calculating the expected delivery date in pregnancy?

Naegele's Rule is a widely accepted method for estimating the expected delivery date in pregnancy. It is based on the premise that a typical pregnancy lasts about 40 weeks (or 280 days) from the first day of the last menstrual period (LMP). According to Naegele's Rule, you take the first day of the last menstrual period, add one year, subtract three months, and then add seven days.

This method leverages the regularity of menstrual cycles and serves as a straightforward tool for healthcare providers to predict the due date for a pregnant individual, which is crucial for prenatal care planning and ongoing monitoring of the pregnancy.

While other methods for calculating delivery dates exist, such as using an ovulation calendar or tracking gestational age and conception dates, they may not provide as standardized or universally applicable an approach as Naegele's Rule. Other methods may depend on more precise timing and data, which can sometimes be less reliable than the information provided by the last menstrual period. Therefore, Naegele's Rule remains a cornerstone in obstetric practice for estimating the expected date of delivery.