Stillbirth rates also increased for gestational ages of 20-27 weeks, 28-31 weeks, 32-33 weeks, 34-36 weeks, 37-38 weeks, and 42-44 weeks.
Commenting on the changes in perinatal and neonatal mortality rates at gestational ages of 34-36 weeks and 37-38 weeks, the authors suggested this may have been the result of recommendations to postpone elective deliveries until 39 weeks.
“A possible reason for the increased mortality at a gestational age of 37-38 weeks could be that physicians may be more likely to defer to 39 weeks for delivery for women at moderately increased risk for adverse perinatal outcomes,” they wrote.
“We found that the decrease in neonatal mortality rates from 2007 to 2015 in the United States was largely associated with changes in the underlying gestational age distribution and less associated with changes in gestational age–specific mortality.”
The researchers reported that they had no conflicts of interest.
SOURCE: Ananth C et al. JAMA Pediatrics. 2018 May 14. doi: 10.1001/jamapediatrics.2018.0249.