Pregnancy Dating

Excerpt

The most important step in the initial evaluation of any pregnant patient is establishing an accurate delivery date or due date (see Image. Pregnancy Timeline). Accurate knowledge of gestational age is important for numerous reasons. A patient's gestational age determines the appropriate intervals for prenatal care visits and the timing of certain interventions (see Image. Birth Weight for Gestational Age Chart). For example, certain antenatal screening tests like the quadruple marker screen (screening test for fetal aneuploidy and open neural tube defects) must be performed with accurate knowledge of the gestational age to accurately calculate lab values. In patients with a history of preterm labor and delivery, screening tests and interventions early in pregnancy can be used to prevent preterm labor in any subsequent pregnancy. As pregnancy progresses, accurate and optimal pregnancy dating is important when deciding on the timing of both medically indicated and elective deliveries.