Early term birth rates declined in the United States, especially among births requiring obstetric interventions, such as labor induction and pre-labor cesarean section delivery, a large retrospective analysis of birth data from multiple countries found.
From 2006 to 2014, the number of early term births (defined as 37-38 weeks gestation) with obstetric intervention fell by over a third, while early term births without obstetric interventions exhibited smaller declines, reported Jennifer L. Richards, MPH, of Emory University in Atlanta, and colleagues.
The rate of late preterm birth (defined as 34-36 weeks gestation) in the U.S. also experienced slightly smaller declines over the same time period, they wrote in the Journal of the American Medical Association.
Over the course of the study period, rates of early term birth fell 35.6% (95% CI 33.3% to 37.8%) among births with clinician-initiated obstetric intervention, while there was a 13.5% decline (95% CI 9.8% to 17.1%) among births without obstetric intervention.
David Hackney, MD, of University Hospitals in Cleveland, characterized this as the most noteworthy finding from the paper.
"This correlates with the efforts of many national and regional organizations to reduce elective or otherwise unnecessary interventions during this time period," Hackney, who was not involved with the research, told MedPage Today via email. "Having administratively worked on this issue myself, it makes one happy to see education and public health campaigns translate into actual broad epidemiologic changes."
Overall, the rates of early term birth in the U.S. decreased from 30.2% to 24.4% from 2006 to 2014. Similar results were seen among early term births with clinician-initiated obstetric interventions (33.0% to 21.1%, respectively), with smaller declines seen even among early term births without obstetric interventions (29.6% to 27.1%, respectively). Obstetric interventions also declined over the time period (48.9% of all early term births in 2006 versus 38.7% in 2014).
"These findings confirm the results of several hospital and regional-based studies reporting declines in elective obstetric interventions at early term gestation and suggest the success of national clinical guidelines aimed at reducing elective deliveries before 39 weeks," Richards told MedPage Today. "For clinicians, it is reassuring that late preterm and early term birth rates appear to be stable or declining in the countries included in this study."
Among examined countries, Canada had the highest rate of early term interventions (42.5% of pregnancies). The U.S. had the highest rate of late preterm interventions (44.1%), but it remained relatively stable over the course of the study period. The rates of late preterm birth also declined slightly in the U.S. from 2006 to 2014 (6.8% to 5.7%, respectively).
An accompanying editorial by Catherine Y. Spong, MD, Acting Director of the National Institute of Child Health and Human Development, argued that interventions are sometimes needed for medically complex pregnancies.
"Although reducing preterm birth is a major goal, sometimes late preterm birth is the best outcome for the mother and/or fetus and these deliveries would require an intervention," she wrote. "Thus, the constant rate of obstetric interventions among late preterm births may be associated with a relatively smaller number of nonindicated late preterm births."
The researchers examined data from live singleton births in the United States, Canada, Denmark, Finland, Norway, and Sweden. During the examined time period, both early term and late preterm birth rates declined in both the U.S. and Norway. Early term birth rates also declined in Sweden. Rates of obstetrical intervention among both late preterm and early term births increased in both Denmark and Finland. Canada had an increase in late preterm birth interventions only.
Hackney noted that the comparisons with other countries are much more difficult to interpret: "Although the authors methodologically do their best there are always going to be differences between countries in measurement accuracy, coding, and, of course, baseline differences in populations."
Limitations to the study include that Danish data were restricted to births through 2010 and Swedish data, to births through 2012. A standardized definition of an obstetrical intervention was applied to each country's birth data, which may not have matched each country's definition of an elective intervention, and there were also limited data on maternal or fetal indications for early delivery.
Richards said the results indicate that efforts to reduce elective deliveries have been successful on a national level, but that the implications of these findings have yet to be fully explored: "There is the caveat that more research is needed to understand potential unintended consequences of delaying the use of interventions, such as whether this comes with increased risk of stillbirth in some cases," she said.
Richards disclosed grant support from the Eunice Kennedy Shriver National Institute of Child Health and Human Development of the National Institutes of Health (NICHD). Other co-authors disclosed grant support from the NICHD, Paris Descartes University, the Japan Society for the Promotion of Science, and the Japan Ministry of Health; and one co-author disclosed grant funding from the Uehara Memorial Foundation, Kanzawa Medical Research Foundation, and the Danone Institute.
Spong disclosed having no conflicts of interest.
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