Subsequent pregnancy in 6 patients with previous peripartum cardiomyopathy resulted in reduction of ejection fraction by >10% in 5 patients at 1 month postpartum. Two patients with impaired ejection fraction at onset of subsequent pregnancy died 3 months postpartum due to heart failure despite optimal medical therapy. Deterioration of left ventricular function occurred uniformly postpartum and was accompanied by elevation of tumor necrosis factor-alpha plasma levels from 2.4 +/- 1.1 pg/ml at onset of subsequent pregnancy to 6.2 +/- 2.4 pg/ml at 1 month postpartum.