Postterm Pregnancy

Pregnancy lasting more than 294 days (42 completed weeks) from the first day of a normal last menstrual period (LMP) or more than 14 days past the estimated date of confinement (EDC) is defined as postterm.1 This definition is somewhat arbitrary and is based on epidemiologic studies demonstrating increased adverse perinatal outcome at late gestational age. This cutoff does not reflect a specific threshold for increased morbidity for the fetus or the mother; indeed, such risks begin to rise before 42 weeks. The terms “post dates” and “prolonged pregnancy” are often used interchangeably with postterm, but are not well defined, and usually refer to pregnancy past 41 weeks. The American Congress of Obstetricians and Gynecologists (ACOG) recommends avoiding these terms given their imprecision. However, there continues to be a significant gap among practicing obstetricians in both accurately defining this condition and managing the complications associated with it. Failure to address this gap may result in adverse neonatal and perinatal outcomes. The goal of this lesson is to update the practicing obstetrician in identifying and caring for these patients.