Rethinking the definition of "term pregnancy".

Term birth (37-41 weeks of gestation) has previously been considered a homogeneous group to which risks associated with preterm (less than 37 weeks of gestation) and postterm births (42 weeks of gestation and beyond) are compared. An examination of the history behind the definition of term birth reveals that it was determined somewhat arbitrarily. There is a growing body of evidence suggesting that significant differences exist in the outcomes of infants delivered within this 5-week interval. We focus attention on a subcategory of term births called "early term," from 37 0/7 to 38 6/7 weeks of gestation, because there are increasing data that these births have increased mortality and neonatal morbidity as compared with neonates born later at term. The designation "term" carries with it significant clinical implications with respect to the management of pregnancy complications as well as the timing of both elective and indicated delivery. Management of pregnancies should clearly be guided by data derived from gestational age-specific studies. We suggest adoption of this new subcategory of term births (early term births), and call on epidemiologists, clinicians, and researchers to collect data specific to the varying intervals of term birth to provide new insights and strategies for improving birth outcomes.