Tuberous sclerosis is an autosomal dominant disorder of hamartoma formation in which manifestations may occur in skin, brain, and viscera. In the past, it was believed that the typical presentation included seizures, mental retardation, and facial angiofibromas ("adenoma sebaceum"). This disorder is now recognized to show wide variability of expression. There are only four cases of tuberous sclerosis in pregnancy in the literature. Two of these had favorable maternal and fetal outcomes and the remaining two presented with serious maternal and fetal complications. These included acute intra-abdominal bleeding due to a ruptured renal tumor, which led to renal failure requiring hemodialysis, and severe preeclampsia with pathologically enlarged kidneys noted at the time of cesarean section. This study presents two more cases of tuberous sclerosis in pregnancy. The first case had renal involvement with bleeding into a renal cyst, renal failure, preeclampsia, and severe intrauterine growth retardation. The second case was complicated by preterm premature rupture of the membranes and preterm labor. Renal involvement appears to be the single most important prognostic factor in pregnancies with tuberous sclerosis. Renal evaluation should be performed in any patient who presents for preconceptional counseling.