1. Indications and Preparations

Pre-Exam Preparation

Determining Estimated Due Date Based on LMP

It is important to estimate the gestational age prior to Obstetric/OB ultrasound assessment to determine if the findings are normal. Naegele’s Rule is a simple way to calculate the due date based on the last menstrual period (LMP) and estimate gestational age prior to the Obstetric/OB ultrasound assessment.

Due Date = Date of first day of last menstrual period (LMP) + 9 Calendar months + 7 days

For example, if the LMP was 7/16/20, add 9 months (4/16/21), then add 7 days = 4/23/21

Gestational age is estimated in weeks from the first day of the LMP. The gestational age as well as the estimated due date can be refined using ultrasound findings which we’ll discuss below.

Leave a Reply

Your email address will not be published. Required fields are marked *