Second-Trimester Ultrasound Receipt Mediates the Relationship Between Public Insurance and Prenatal Diagnosis of a Congenital Heart Defect.

Objective: To delineate the mechanism behind insurance-related disparities in the prenatal diagnosis of a congenital heart defect (CHD).

Methods: This was a retrospective analysis of electronic health records of pregnant individuals whose infants received CHD surgery between 2019 and 2020 in the third-largest United States metropolitan area. The outcome was whether a prenatal diagnosis was received. The exposure was the pregnant individual's insurance status. The mediator was second-trimester ultrasound receipt. Control variables included sociodemographic and clinical characteristics of the pregnant individual and infant. The relationships between exposure, mediator, and outcome were quantified using mediation analysis with multivariable fixed-effects regression.

Results: In total, 496 pregnant individuals met inclusion criteria; 215 (43.3%) were publicly insured and 305 (61.5%) had prenatal diagnosis. In bivariate regressions, public insurance was associated with a 12.6% lower probability (CI 3%-21%) of prenatal diagnosis. In multivariable models, public insurance was associated with 13.2% lower probability (CI 2%-25%) of second-trimester ultrasound receipt but was no longer associated with prenatal diagnosis after adjusting for second-trimester ultrasound receipt, suggesting a possible mediation effect. Mediation analysis confirmed that second-trimester ultrasound receipt mediated 39% of the relationship between public insurance and prenatal diagnosis.

Conclusion: An appreciable portion of insurance-related differences in prenatal CHD diagnosis is due to the lower frequency of second-trimester ultrasound receipt among those with public insurance.