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187: Timing of delivery for chronic hypertension: a population-based cohort study in the United States

      Objective

      The objective of this analysis was to determine gestational age-specific labor induction trends in the United States for pregnancies complicated by chronic hypertension.

      Study Design

      This population-based study of U.S. natality records from 2006-2013 evaluated early term (≥37 to <39 weeks gestational age) versus full term inductions (≥39 to 40 weeks gestational age) amongst primiparous women with chronic hypertension. Obstetrical, medical, and demographic characteristics were evaluated. Multivariable log-linear regression models were developed to determine factors associated with induction. Neonatal outcomes including low Apgar score and neonatal intensive care unit (NICU) admission were also compared based on gestational age of induction.

      Results

      15,446 pregnancies were included in the analysis. The proportion of full-term relative to early-term inductions increased significantly over the study period. For chronic hypertension the proportion of full-term inductions increased from 53.3% to 64.8% (FIGURE). These increases retained significance in the adjusted log linear regression models. Full-term delivery was associated with significantly decreased risk for low Apgar scores and NICU admission compared to early term delivery.

      Conclusion

      Induction at full term is becoming increasingly prevalent for women with chronic hypertension. Given that delivery timing includes balancing benefits of neonatal delivery at full term versus risk of stillbirth the last few weeks of pregnancy, future comparative effectiveness research to identify delivery-timing strategies is urgently needed.
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