MacDorman and associates studied this issue using a different approach.9 They mined National Center for Health Statistics fetal death and live birth data for 2006 and 2012 to compute gestational age-specific stillbirth rates ≥ 20 weeks using 2 methods: 1) a “traditional” technique that measured the ratio of the number of stillbirths at a given gestational age divided by the number of live births plus stillbirths at that gestational age, x 1000; and 2) a “prospective” method that measured the ratio of stillbirths at a given gestational age divided by the number of live births plus stillbirths at that gestational age or greater, x 1000. The authors posited that the prospective method was superior because it gave a good approximation of the number of women still pregnant and thus at risk of subsequent stillbirth at a given gestational age.
They found that between 2006 and 2012, the percent distribution of live births at 34 to 38 weeks decreased by 10%–16%, while births at 39 weeks increased by 17%, consistent with efforts at reducing both elective preterm and early term deliveries. While the traditional method showed an increase in stillbirths at 34 to 36, 37, and 38 weeks, these rates were influenced by decreases in live births at those gestational ages. In contrast, there were no differences in prospective stillbirth rates at 21 to 42 weeks, leading the authors to conclude that “preventing non-medically indicated deliveries before 39 weeks of gestation did not increase the stillbirth rate at the national level.”
Taken together, the findings from these 2 studies provide some reassurance that efforts to reduce neonatal morbidity and mortality putatively caused by elective early term deliveries have not increased stillbirth rates.
What about neonatal morbidity and mortality?
But are elective early term deliveries clearly linked to excess neonatal morbidity and mortality? Salemi and associates addressed this question in a population-based retrospective cohort study of 675,302 singleton infants born alive at 37 to 44 weeks’ gestation from 2005 to 2009 in more than 125 birthing facilities in Florida.10 They excluded pregnancies with maternal medical or obstetrical complications, history of substance abuse, or neonatal congenital anomalies. Five subgroups were analyzed: 1) early (37-38 weeks) elective induction (4.9%); 2) early elective cesarean deliveries (8.2%); 3) early spontaneous deliveries (16.7%); 4) early medically indicated deliveries (3.4%); and 5) delivery at 39 to 40 weeks (60.7%), which served as the control group.