Fetal catecholamine responses to vibroacoustic stimulation.

Abstract

The aim of this study was to determine whether fetal vibroacoustic stimulation caused a surge of catecholamines from the fetal sympathoadrenal system. A randomized, prospective, controlled trial was performed at The Queen Mother's Hospital, Glasgow. Circulating catecholamine levels in cord blood from a group of fetuses who received vibroacoustic stimulation 1 to 2 minutes before delivery by elective cesarean section (n = 25) were compared with those from a group of controls (n = 23) (Mann-Whitney U test). Fetal heart rate response to vibroacoustic stimulation was recorded in 10 additional pregnancies under identical experimental conditions. No differences were found in norepinephrine or epinephrine levels between the vibroacoustic stimulation group and the control group. A positive fetal heart rate response was observed in seven of 10 fetuses tested. Fetal norepinephrine levels were also found to be influenced by maternal blood pressure and administration of ephedrine. Under these conditions vibroacoustic stimulation does evoke the characteristic fetal heart rate response, but it does not induce a surge of catecholamines from the fetal sympathoadrenal system. Therefore it is unlikely that the immediate fetal heart rate response to vibroacoustic stimulation is induced by a surge in systemic catecholamines.