Objectives. This study sought to determine risks and outcome of pregnancy and delivery after the modified Fontan operation.Background. Increasingly, female Fontan patients reaching child-bearing years are interested in having children. To date, the number of reported pregnancies is small, and pregnancy has therefore been discouraged.Methods. One hundred ten of 126 female patients from the Fontan registries of the Mayo Clinic and University of California Los Angeles Medical Center responded to a mailed questionnaire. An additional six patients with a reported pregnancy from other centers were identified and reviewed to assess pregnancy outcomes.Results. Among the participating centers, a total of 33 pregnancies after Fontan operation for various types of univentricular heart disease were reported. There were 15 (45%) live births from 14 mothers, with 13 spontaneous abortions and 5 elective terminations. In the 14 women with live births, the median number of years between operation and pregnancy was 4 (range 2 to 14). Reported prepregnancy problems in these gravidas included atrial flutter in one patient and ventricular dysfunction, aortic regurgitation and atrioventricular valve regurgitation in another. One patient developed supraventricular tachycardia during pregnancy and had conversion to sinus rhythm. No maternal cardiac complications were reported during labor, delivery or the immediate puerperium. There were six female and nine male infants (mean gestational age 36.5 weeks; median weight 2,344 g). One infant had an atrial septal defect. At follow-up, mothers and infants were alive and well.Conclusions. Pregnancy after the Fontan operation appears to have been well tolerated in 13 of 14 gravidas. There does appear to be an increased risk of miscarriage. The tendency to routinely discourage pregnancy may need to be reconsidered.