Blunted fetal response to vibroacoustic stimulation following chronic exposure to propranolol.

A recent, prospective randomized trial has suggested that long-term use of prophylactic beta-adrenergic blocking agents may slow the rate of aortic dilation in those patients with Marfan's syndrome exhibiting evidence of existing dilation. Accordingly, administration of such medication from the midtrimester onward has been advocated in these patients. Acute oral administration of propranolol (80 mg) has been shown to depress fetal heart rate response to vibroacoustic stimulation. We present a case in which chronic administration of propranolol 150 mg/day to a patient with Marfan's syndrome with existing aortic root dilation was associated with repeated abnormal intrapartum fetal heart rate responses to vibroacoustic stimulation. Subsequent delivery of a nonhypoxic, nonacidotic infant suggests that maternal administration of beta-blockers should be considered in the interpretation of results of fetal vibroacoustic stimulation. This case also supports that in similar clinical presentations, ultrasonographic confirmation of the fetal startle response, or alternatively observation of the resulting fetal recoil may be utilized rather than the fetal heart rate, which may be modulated by maternal medications.