About
The Pregnancy Due Date Calculator is a clinical tool used to estimate the expected date of delivery (EDD), gestational age, and estimated date of conception. Pregnancy dating may be estimated based on the last menstrual period (LMP), ultrasound-estimated gestational age, known conception date, or assisted reproductive technology (ART) information, including the embryo transfer date and embryo age at transfer. Accurate pregnancy dating is important for monitoring fetal growth and development, timing prenatal screening and diagnostic testing, interpreting pregnancy-related findings, and planning obstetric care and delivery. The most appropriate dating method depends on the clinical circumstances and the reliability of the available information. LMP-based dating traditionally assumes a 28-day menstrual cycle with ovulation occurring on day 14 and may be adjusted when the patient’s cycle length differs from 28 days. Its accuracy may be limited when menstrual cycles are irregular or the LMP is uncertain. Ultrasound-based dating estimates the EDD from the gestational age determined at the time of ultrasound, with earlier ultrasound examinations generally providing more accurate pregnancy dating. In pregnancies resulting from ART, the EDD may be calculated from the embryo transfer date and embryo age at transfer, providing a more precise basis for pregnancy dating.