Thank you for your interest in our article. Last month, the American College of Obstetricians and Gynecologists and the Society of Maternal Fetal Medicine published a joint statement to redefine what is considered a full-term pregnancy . The early-term period is now defined as 37 weeks 0 days to 38 weeks 6 days’ gestation, and the full-term period is now defined as 39 weeks 0 days to 40 weeks 6 days’ gestation. The impetus for this change is the emerging evidence that newborn outcomes are not uniform after 37 weeks’ gestation.

Our study results are in keeping with the emerging evidence that early term deliveries have outcomes that are different from deliveries after 39 weeks’ gestation. Although previous studies have focused mostly on neonatal differences between early term and full-term newborn infants, our study suggests that the differences are not solely among neonates and may have implications for future pregnancies.

Although we know a previous preterm birth (PTB) is a risk factor for a subsequent PTB, the same was not felt to be true if a patient had a previous full-term birth, defined as ≥37 weeks’ gestation. We found, however, a 3-fold higher risk of spontaneous PTB (sPTB) in a subsequent pregnancy if a woman had spontaneous labor and delivery in the early-term period with the previous pregnancy.

We specifically did not evaluate chorioamnionitis as a contributing factor for early-term births in the index pregnancy or sPTB in a subsequent pregnancy. However, the presence or absence of chorioamnionitis would not alter the results of the study. Regardless of whether chorioamnionitis is a contributing factor that leads to the increased risk of early term births and subsequent sPTB, this newly identified group of women (those with a previous early-term spontaneous delivery) appear to be at risk for sPTB in a subsequent pregnancy, and further evaluation of this group is warranted.

The redefining of what is considered full term is a shift in what has been long-held to be true in obstetrics. However, just as there has been a change in practice with preventing nonmedically indicated deliveries at <39 weeks’ gestation, so too might there be a change in practice considering a previous term delivery “protective” if it occurred in the early-term period. Additionally, an evaluation of our current interventions to reduce subsequent sPTB may be warranted in those who had a previous early-term birth.