Trends in provider-initiated versus spontaneous preterm deliveries, 2004-2013

The objectives of this study were as follows: (i) to estimate the proportion of preterm deliveries at a tertiary perinatal center that were provider-initiated versus spontaneous before and after a 2009 policy to reduce elective early-term deliveries, and (ii)to evaluate whether shifts in type of preterm delivery varied by race/ethnicity.

We performed a retrospective cohort study of preterm deliveries over a 10-year period, 2004 to 2013, including detailed review of 929 of 5566 preterm deliveries, to designate each delivery as provider-initiated or spontaneous. We dichotomized the time period into early (2004 to 2009) and late (2010 to 2013). We used log-binomial regression to calculate adjusted risk ratios.

Of the 46 981 deliveries, 5566 (11.8%) were preterm, with a significant reduction in the overall incidence of preterm delivery from 12.3 to 11.2% (P=0.0003). Among the 929 preterm deliveries analyzed, there was a reduction in the proportion of provider-initiated deliveries from 48.3 to 41.8% that was not statistically significant. The proportion of provider-initiated preterm deliveries among Black, but not White, women declined from 50.8 to 39.7% (adjusted relative risk: 0.66; 95% confidence interval (CI): 0.45 to 0.97). This coincided with a larger reduction in overall preterm deliveries among Black women (16.2 to 12.8%) vs White women (12.3 to 11.2%) (P interaction=0.038). By 2013, the incidence of preterm deliveries had decreased for both Black (12.1%) and White women (11.4%), and the difference was no longer statistically significant (P=0.7).

We found a reduction in preterm deliveries after a policy targeted at reducing elective early-term deliveries in 2009 that coincided with reductions in the proportion of provider-initiated preterm deliveries, especially among Black women.