Trends in prematurity: what do changes at an urban institution suggest about the public health impact of 17-alpha hydroxyprogesterone caproate?

Despite the introduction of 17-alpha-hydroxyprogesterone caproate (17P), the national preterm birth (PTB) rate remains unchanged. Our objectives were to determine whether the overall rate of PTB has decreased and whether there has been a shift in the trends of prematurity at our institution since the initiation of 17P use. We performed a cross sectional study of the PTB rate and gestational age distribution at delivery (GA-del) at our institution over two, 2-year time periods: TP1 (pre 17P, 1 Jan 2004-31 Dec 2005) and TP2 (post 17P, 1 Jan 2008-31 Dec 2009). Statistical analyses included χ(2) tests for categorical data, t-tests for continuous data, and multivariable logistic regression to control for confounders. Overall (n = 15,421), there was no difference in the rate of PTB from TP1 to TP2 (16.65 vs 16.95%, p = 0.62). Among those with a history of prior PTB (n = 2,141), the mean preterm GA-del was 10 days later in TP2 than in TP1 (33.13 vs 31.64 weeks, p < 0.01) and significantly more preterm infants in TP2 delivered between 34-36 6/7 weeks than in TP1 (65.00 vs 45.63%, p < 0.01). The odds of a preterm infant delivering in the late preterm period was 2.3-fold higher in TP2 than TP1 (95% CI 1.49-3.54) after controlling for confounders. The significant shift in GA-del towards the late preterm period in TP2 may be due to the introduction of 17P use at our institution. Additional studies are needed to determine whether these trends persist on a nationwide level.