Background: Cardiomyopathies, particularly peripartum cardiomyopathy (PPCM), significantly contribute to maternal morbidity in the United States. Objectives: The authors estimated the prevalence and mortality of PPCM and other cardiomyopathies (OCMs) during pregnancy among women aged 15 to 55 years from 2010 to 2020 in the United States using a cross-sectional analysis of multiple data sets. Methods: We identified PPCM, OCM, and deliveries using International Classification of Diseases and diagnosis related group codes in the National Inpatient Sample. We calculated PPCM and OCM prevalence and adjusted prevalence ratios (aPRs) by select covariates. We identified pregnancy-related deaths from all cardiomyopathies combined and PPCM exclusively from 2015 to 2020 Pregnancy Mortality Surveillance System. We calculated pregnancy-related mortality ratios (PRMR) by select covariates. Results: The overall PPCM and OCM prevalence were 105.1 (95% CI: 101.8-108.3) and 76.1 (95% CI: 73.6-78.7) cases per 100,000 delivery hospitalizations, respectively. PPCM prevalence increased with advancing maternal age and decreasing neighborhood income and exhibited marked differences among Black and American Indian or Alaska Native women (aPR: 3.58 [95% CI: 3.36-3.82] and aPR: 1.96 [95% CI: 1.57-2.45], respectively). PPCM prevalence was higher among those with chronic hypertension and diabetes (aPR: 12.17 [95% CI: 11.51-12.88] and aPR: 6.25 [95% CI: 5.77-6.78], respectively). The overall cardiomyopathy and PPCM PRMR were 2.1 and 1.0 deaths per 100,000 live births, respectively. PRMR were highest among those aged ≥40 years and among American Indian and Black women (overall cardiomyopathy PRMR: 7.3, 6.0 deaths per 100,000 live births respectively). Conclusions: Intensifying efforts to address cardiomyopathies and enhance cardiovascular health before, during, and following pregnancy may reduce the burden of maternal morbidity. © 2025 The Authors