National trends and racial differences in late preterm induction

Objective: The objective of the study was to determine the trends and racial differences in late preterm induction (LPI) of labor in the United States. Study Design: Data from the National Vital Statistics System were used to identify women eligible for induction between 34 and 42 weeks' gestation from 1991 to 2006. Annual LPI rates were calculated, and maternal race/ethnicity was classified into 4 groups. Changes in the frequency and odds of LPI, stratified by race/ethnicity, were assessed using logistic regression. Results: Among the 42.0 million eligible women, LPI rates increased from 0.46% to 1.37% (P <.01) over 16 years. LPI rates were highest for black women (P <.01) each year, and after adjusting for confounding factors, the odds of LPI were highest (P <.01) and rose most rapidly (P <.01) for black women (non-Hispanic white: odds ratio [OR], 1 [referent]; Hispanic white: OR, 0.76; black: OR, 1.31; other: OR, 0.81; P <.01). Conclusion: LPI rates were persistently highest and rose most rapidly for black women.