BACKGROUND: The associated risk of elevated levels of maternal serum human chorionic gonadotropin (MShCG) with pregnancy complications was reported in many studies. However, the outcome of pregnancies with extremely high levels of MShCG was never independently studied. METHODS: We report on 6 out of 45,990 studied patients with extremely high levels of MShCG (>15 multiples of the medians) analyzed during the second trimester. RESULTS: Although our patient population was composed of more Jewish than Arab pregnant women, all those patients were Arabs. Overall, the prognosis of those pregnancies was poor. In 1 case, an antepartum fetal death occurred, 2 had premature deliveries (one of the newborns had severe failure to thrive), and 2 delivered small for gestational age babies. In 5 of these 6 cases, no specific diagnosis was established. One case was complete hydatidiform mole with a coexisting normal fetus. CONCLUSIONS: We recommend that these patients undergo counseling in which the predicted outcome will be described. In addition, a follow-up of high-risk pregnancy should be implemented: sonographic evaluation should be performed, initially to rule out a molar gestation. The patients should then be followed for growth restriction and they should be monitored to rule out other pregnancy complications such as premature labor and antepartum fetal death. Finally, the overrepresentation of Arabs among our affected patients raises the question of a possible genetic tendency for increased MShCG levels especially in the extreme level group.