Method for estimating due date

Data from the last menstrual period (LMP) and first accurate ultrasound should be used to establish an estimated due date (EDD). This should be documented in the medical record and serve as the basis for determining the best obstetric estimate for gestational age for the purpose of clinical care.

If the pregnancy resulted from assisted reproductive technology (ART), the ART-derived gestational age should be used to assign the EDD (Table 1).