​Summary: Having health insurance is associated with improvements in health care access and use, health behaviors, and outcomes. Authors examined changes in health insurance coverage for California women before, during, and after pregnancy after implementation of the Affordable Care Act (ACA).

Authors used data from the 2011–2017 California Maternal and Infant Health Assessment, an annual representative survey of women sampled from birth certificates. They examined health insurance coverage at baseline before ACA implementation (2011–2013) and in each survey year from 2014 to 2017 for 3 periods (before, during, and after pregnancy). Authors calculated prevalence ratios to evaluate changes in health insurance coverage, adjusting for changes in demographic characteristics. Few women were uninsured during pregnancy before implementation of the ACA; therefore, analyses focused on health insurance before pregnancy and postpartum.

Findings: Before ACA implementation, 24.4% of women reported being uninsured before pregnancy, which decreased to 10.1% in 2017. About 17% of women reported being uninsured postpartum before ACA implementation, and this percentage decreased to 7.5% in 2017. ACA implementation resulted in a >50% adjusted decline in the likelihood of being uninsured before pregnancy or postpartum, primarily because of substantial increases in Medicaid coverage.

ACA implementation resulted in a dramatic reduction in mothers in California who were uninsured before and after pregnancy. Medicaid expansion played a major role in this improvement.