OBJECTIVES: To estimate the incidence, describe the mortality, and identify independent predictors of peripartum cardiomyopathy, a very serious cardiovascular complication of pregnancy associated with maternal morbidity and mortality among otherwise healthy women without prior heart disease. METHODS: We identified all cases of diagnosed heart failure that occurred among women within 1 month before to 5 months after delivery of a liveborn neonate in Kaiser Permanente Northern California delivery hospitals between 1995 and 2004. Incident peripartum cardiomyopathy was confirmed from medical records documenting dilated cardiomyopathy with reduced left ventricular systolic function after excluding women with prior heart failure or valvular disease. Data sources included medical records, electronic clinical databases, and state birth and death files. RESULTS: Among 227,224 eligible women, we confirmed 110 recognized peripartum cardiomyopathy cases (incidence: 4.84 per 10,000 live births, 95% confidence interval 3.98-5.83). Independent predictors included maternal age of 25 years or older, non-Hispanic African American and Filipino groups, parity of 4 or greater, multiple gestation, severe anemia, pre-existing and pregnancy-related hypertensive disorders, and hemolysis, elevated liver enzymes, low platelets syndrome. Maternal death rate (per 1,000 person-years) was higher among cases (6.12) than noncases (0.23; P<.001). Neonates whose mothers developed peripartum cardiomyopathy experienced poorer clinical outcomes. CONCLUSION: Within a large, diverse northern California population, 1 of every 2,066 women delivering a liveborn neonate had recognized, confirmed peripartum cardiomyopathy, which was associated with higher maternal and neonatal death rates and worse neonatal outcomes. Several readily available patient characteristics can be used to identify women at risk for this severe pregnancy complication. LEVEL OF EVIDENCE: II.