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What is a term pregnancy?

In humans, singleton (one-baby) pregnancy lasts, on average, 40 weeks, or 280 days from the first day of the last menstrual period, which this is how doctors determine the estimated due date. By comparison, elephants can be pregnant for up to two years.

Until recently, anyone between 37 to 42 weeks of pregnancy was considered “term” and safe to deliver. This conventional wisdom existed because it was believed that the outcomes for both the baby and the mother during this interval of time were uniform and good, or safe with few risks. However, a large amount of research has now shown this is not uniform during these five weeks, and risks can exist from both a maternal and neonatal standpoint. As a result, in 2012, a group of professional societies convened and redefined what exactly “term” means, and provided recommendations regarding delivering for medically indicated and non-medically indicated circumstances. In addition, national initiatives now exist to decrease complications to babies and the mothers when delivery occurs too early without a medical reason.

In defining term pregnancy, it is now recommended to use the following: Early term is between 37 weeks through the 38th week, full term is 39 weeks through the 40th week, late term is 41 weeks up to the 42nd week and post term is greater than 42 weeks. The American Congress of Obstetricians and Gynecologists, The Society for Maternal Fetal Medicine, and many neonatal and pediatric societies support these definitions as well.

These definitions are important because research shows that adverse neonatal outcomes, especially regarding respiratory issues, is the lowest among uncomplicated pregnancies delivered between 39 weeks of gestation and through the 40th week. Lung development continues into early childhood, and elective early term deliveries increase the incidence of respiratory distress syndrome, ventilator use, infections such as pneumonia, respiratory failure, NICU admissions, low blood sugar, decreased APGAR scores and possibly infant mortality. Unless one enters labor naturally, or a medical reason exists for early term delivery, elective delivery prior to 39 weeks is discouraged.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.