For decades, peripartum cardiomyopathy has remained an enigma. Despite extensive research, our understanding of how a previously healthy woman can develop lethal heart failure in the context of pregnancy remains vague. Recent work suggests that inadequacy of the cardiac microvasculature may be the primary abnormality and has implicated an antiangiogenic fragment of the nursing hormone prolactin as playing an important role. In this issue of the JCI, Halkein et al. explore signaling downstream of this prolactin fragment and demonstrate that miR-146a is a critical mediator of the antiangiogenic effects in endothelial cells. In addition, the study uncovers unexpected exosomal transfer of this microRNA to cardiomyocytes that may affect myocardial metabolism.