Identification of Chronic Hypertension in Pregnancy in Three Administrative Data Sources Among Medicaid-Funded Births in California.

Purpose: Administrative data sources are used to describe the epidemiology of chronic hypertension in pregnancy and its consequences. Differences in identification across sources may affect research estimates. We compared identification of chronic hypertension in birth certificate records, hospital discharge records, and Medi-Cal claims in the same individuals.

Methods: We used data from 820 140 2016-2020 California Medi-Cal covered births. We identified chronic hypertension on birth certificates using the prepregnancy hypertension check box and in hospital discharge records and Medi-Cal claims using ICD codes. We compared the prevalence of chronic hypertension and identified predictors of agreement. We also compared absolute and relative estimates of racial/ethnic disparities in chronic hypertension and associations with neonatal outcomes.

Results: The prevalence of chronic hypertension was 0.7% in birth records, 2.1% in hospital discharge records, and 3.9% in Medi-Cal claims. There was low to fair agreement between birth certificate records and hospitalization records (kappa = 0.36) and Medi-Cal claims (kappa = 0.25). Characteristics associated with the worst agreement were eligibility for Women Infant and Children benefits, US-born, and normal body mass index. Estimates of the relative risk for racial/ethnic disparities and associations with preterm birth and SGA age at delivery were similar across sources. Estimates of risk differences were larger in hospitalization and Medi-Cal claims data.

Conclusions: Reliance on birth certificate data may contribute to underestimated prevalence estimates and biased causal estimates. Epidemiologic research and public health surveillance of chronic hypertension and its consequences should incorporate data from multiple data sources to improve validity of estimates.