Accurate knowledge of the gestational age is important for numerous reasons. A patients gestational age determines the appropriate intervals for prenatal care visits, as well as the timing of certain interventions. This activity describes the different methods to date a pregnancy.

What is the most accurate measurement for dating a pregnancy?

Ultrasound measurement of the embryo or fetus in the first trimester (up to and including 13 6/7 weeks of gestation) is the most accurate method to establish or confirm gestational age.

How accurate are due dates for first babies?

But data from the Perinatal Institute, a non-profit organisation, shows that an estimated date of delivery is rarely accurate - in fact, a baby is born on its predicted due date just 4% of the time.