Differences in Preterm Births by State Reproductive Rights Policy Environment: Findings From the 2022 National Vital...

This study analyzed the extent to which variations in state preterm birth rates are associated with state reproductive rights policies after accounting for individual risk factors.

The study analyzed preterm (<37 weeks) births using the 2022 National Vital Statistics System Natality File. State reproductive rights policy scores were obtained from the Institute for Women's Policy Research (IWPR) 2022 Reproductive Rights Index. IWPR scores were trichotomized to reflect approximately one-third of births occurring in most-restrictive, somewhat-restrictive, and least-restrictive states. Logistic regression was used to estimate the likelihood of preterm birth, testing the independent significance of state reproductive rights restrictions after adjusting for maternal characteristics. Sensitivity analyses adjusted for other state characteristics.

Among 3,530,543 births analyzed, mean preterm birth rates ranged from a mean of 9.4% in the group of the least-restrictive states to a mean of 11.2% in the group of most-restrictive states. The highest rates were in Mississippi (14.3%), Louisiana (13.3%), and West Virginia (13.3%), all in the most-restrictive category. There was an r = .54 correlation between state IWPR scores and preterm birth percentage (p < .001). After adjusting for sociodemographic and clinical risk factors, births in the most-restrictive states had 20% higher and somewhat-restrictive states had 16% higher odds of preterm birth as compared with births in the least-restrictive states, with state rankings attenuated but remaining significant after inclusion of other state characteristics.

Although this study cannot establish causal inference, restrictive reproductive rights may be linked to prematurity through higher rates of unintended pregnancy and greater maternal comorbidity. Study findings add to a growing literature on health status differences between states associated with restrictive reproductive rights legislation.