Geographic variation in induction of labor at 39-weeks in low-risk nulliparas across the United States

Abstract

To investigate geographic variation in induction of labor (IOL) at 39-weeks gestation in low-risk nulliparas across the U.S. Data was collected from 2020 U.S. Vital Statistics birth certificates. Inductions and cesarean deliveries (CD) were examined in “low-risk” term (39-42 weeks of gestation) nulliparas, where “low-risk” was defined as patients without gestational or pre-gestational diabetes, chronic hypertension, or hypertensive disorders of pregnancy whose neonate was a vertex-presenting, non-anomalous singleton with birthweight 2500 to 5000 grams. We analyzed variation in 39-week induction rates in this population and whether this varied by various geographic regions, including the states, census divisions, and metro and urban characterization. We explored whether this variation was correlated to variation in cesarean delivery using Spearman Correlation testing. P-values < 0.05 were considered statistically significant. Rates of overall induction of labor at 39-42 weeks varied widely, from 14.2% to 59.1% across states (median 39.8%; IQR 37.0-49.0%). Similarly, rates of labor induction at 39 weeks specifically varied across states from 6.8% to 38.3% (median 17.9%; IQR 12.9-23.4%). Total induction rates and 39-week inductions rates were highly correlated across states (weighted Spearman correlation coefficient 0.90; p< 0.01) (Figure). Cesarean deliveries varied across states from 15.5% to 28.1%; however, this variation was not correlated with the variation in either total or 39-week inductions (p=0.61 and p=0.17, respectively). There was wide variation in 39-week induction rates at every geographic level (Table), varying up to 3-fold across census division from 9.7% in the Pacific to 30.2% in the East South Central. There is significant variation in rates of induction of labor at 39-weeks in low-risk nulliparous patients across the US. While this did not appear to correlate with variation in cesarean delivery, the reasons for this wide practice variation and implications on health and resource utilization should be further explored.View Large Image Figure ViewerDownload Hi-res image Download (PPT)