To evaluate challenges facing heart transplant recipients who become pregnant, we surveyed 194 heart transplantation centers and reviewed the literature. Thirty-two known pregnancies in heart (n = 29) or heart-lung (n = 3) allograft recipients have resulted in 29 children, including two sets of twins. The method of delivery was most often vaginal (cesarean section rate was 33%), and premature delivery was common (41%). The onset of pregnancy from the time of transplantation was 2.6 +/- 0.3 years, with the age at conception ranging from 19 to 35 years. Hypertension (44%), premature labor (30%), and preeclampsia (22%) were the most frequent maternal complications. Four patients experienced a worsening of ongoing chronic renal insufficiency; four patients experienced infections during pregnancy, and six patients (22%) were successfully treated for rejection episodes during pregnancy by adjustments in standard immunosuppressive agents. No peripartum deaths were reported; three late deaths occurred. Of the 29 children born of heart transplant recipients who became pregnant, no fetal anomalies or neonatal deaths occurred. Prematurity (41%) and low birth weight (17%) were the most common complications. All children are reported in good health at 3.4 +/- 0.4 years of age. Most transplant recipients (59%) were being treated with triple-drug immunosuppression with azathioprine, corticosteroids, and cyclosporine during pregnancy. The most common alteration to immunosuppressive therapy during pregnancy (41%) involved increasing cyclosporine doses caused by decreasing cyclosporine levels during pregnancy. Twenty-two percent of patients underwent empiric lowering of cyclosporine doses during pregnancy; four patients continued with corticosteroid tapering during pregnancy, and four patients increased corticosteroid doses.(ABSTRACT TRUNCATED AT 250 WORDS)