Variation in Restrictive Abortion Policies and Adverse Birth Outcomes in the United States from 2005 to 2015.

Background: Since 2011, U.S. states have enacted more than 400 policies restricting abortion access. As structural determinants, abortion policies have the potential to influence maternal and child health access, outcomes, and equity through multiple mechanisms. Limited research has examined their implications for birth outcomes.

Methods: We created a state-level abortion restrictiveness index composed of 18 restrictive abortion policies and evaluated the association between this index and individual-level probabilities of preterm birth (PTB) and low birthweight (LBW) within the United States and by Census Region, using data from the 2005-2015 National Center for Health Statistics Period Linked Live Birth-Infant Death Files. We used logistic multivariable regression modeling, adjusting for individual- and state-level factors and state and year fixed effects.

Results: Among 2,500,000 live births, 269,253 (12.0%) were PTBs and 182,960 (8.1%) were LBW. On average from 2005 to 2015, states had approximately seven restrictive abortion policies enacted, with more policies enacted in the Midwest and South. Nationally, relationships between state restrictiveness indices and adverse birth outcomes were insignificant. Regional analyses revealed that a 1 standard deviation increase in a state's restrictiveness index was associated with a 2% increase in PTB in the Midwest (marginal effect [ME], 0.25; 95% confidence interval [CI], 0.04-0.45; p < .01), a 15% increase in LBW in the Northeast (ME, 1.24; 95% CI, 0.12-2.35; p < .05), and a 2% increase in LBW in the West (ME, 0.12; 95% CI, 0.01-0.25; p < .05).

Conclusion: Variation in restrictive abortion policy environments may have downstream implications for birth outcomes, and increases in abortion restrictions were associated with adverse birth outcomes in three out of four Census Regions.