Why do some recovered peripartum cardiomyopathy mothers experience heart failure with a subsequent pregnancy?

After concerns about survival and recovery from peripartum cardiomyopathy (PPCM), the question commonly asked is, "Is it safe to have another pregnancy?" While important advances have been made in the past decade in the recognition and treatment of PPCM, we still do not know why some apparently recovered PPCM mothers have a relapse of heart failure in a subsequent pregnancy. Knowing that some risk for relapse is always present, careful monitoring of the post-PPCM pregnancy is currently the best way to enable earlier diagnosis with institution of effective evidence-based treatment. In that situation it is reassuring to observe that when a subsequent pregnancy begins with recovered left ventricular systolic function to echocardiographic ejection fraction ≥0.50, even with relapse, the response to treatment is good with much more favorable outcomes. On the other hand, beginning the subsequent pregnancy with echocardiographic ejection fraction <0.50 greatly increases the risk for less favorable outcomes. This article summarizes the current state of knowledge; addresses the important questions facing patients, their families, and caregivers; and identifies the need for a prospective multi-center study of women with post-PPCM pregnancies. The reality is that an estimated 10 % to 20 % of apparently recovered PPCM mothers are going to relapse in a post-PPCM pregnancy; but we do not yet know why. Nevertheless, the lowest risk for relapse is experienced by those who (1) recover to left ventricular ejection fraction 0.55 prior to another pregnancy; (2) have no deterioration of left ventricular ejection fraction after phasing out angiotensin-converting enzyme inhibitor/angiotensin-receptor blocker treatment following recovery; and perhaps, (3) demonstrate adequate contractile reserve on exercise echocardiography.