Obstetric interventions are changing the gestational age distribution of US births

Obstetric interventions such as increases in the use of induction of labor (IOL) and use of cesarean deliveries is shifting gestational age distributions of births in the U.S. A new study, which showed that IOL and cesarean delivery are increasingly being used at 37-39 weeks of gestational age, regardless of an increase in maternal risk for interventions, is published in the Journal of Women's Health.

Ryan Masters, from the University of Colorado Boulder, and co-authors reported that between 1990 and 2017, the percent of singleton first births occurring between 37 and 39 weeks gestation increased from 38.5% to 49.5%.

"The changes were driven by increases in IOL and a shift in the use of cesarean deliveries toward earlier gestations," stated the authors. "The changes were observed among all racial/ethnic groups and all maternal ages, an across all U.S. states. The same changes were also observed among U.S. women at low risk for interventions."

"The fact that these changes were observed among women at low risk for interventions implies that these interventions were elective and not increased in response to a rise in high-risk pregnancies," says Journal of Women's Health Editor-in-Chief Susan G. Kornstein, MD, Executive Director of the Virginia Commonwealth University Institute for Women's Health, Richmond, VA. "An increase in early-term births can be problematic."