The use of beta-adrenergic antagonists for the control of high blood pressure associated to pregnancy is frequent. Their use is related with the appearance of undesirable effects of the fetus. The case of neonatal cardiac arrest attributed, to the administration of labetalol to the mother is presented. The high transplacentary passage, the different pharmacokinetics of the drug in the newborn and the clinical evolution of the patient suggests its involvement. It is concluded that labetalol may cause severe undesirable effects in newborns and fetal heart rate of the mother and neonate should be monitored upon use of this drug.