Alcohol delays the emergence of the fetal elicited startle response, but only transiently.

Prenatal exposure to alcohol may exert a significant detrimental effect on the functioning of the individual's brain, however few studies have examined this before birth. This longitudinal study examined the effect of maternal alcohol consumption on the elicited startle response of the fetus. Two groups of fetuses were examined: one whose mothers drank alcohol (approximately 10 units per week); the other whose mothers did not drink alcohol. Fetuses were examined at 29, 32 and 35 weeks gestation and their startle response observed using ultrasound in response to 2 presentations of a pink noise (70-250Hz) at 90dB(A) separated by 30s. Fetuses exposed to alcohol exhibited a weaker startle response at 29 weeks gestation than did fetuses not exposed to alcohol. There was no difference in the response at 32 and 35 weeks gestation. To ensure that the effects were not due to a more general effect of alcohol on fetal movement, a second experiment compared the spontaneous movements (observed on ultrasound for 45 min) of fetuses whose mothers drank alcohol and fetuses of mothers who didn't drink alcohol. There were no differences in movements exhibited by the fetuses. The results suggest that exposure to alcohol delays the emergence of the elicited startle response at 29 weeks gestation but this delay has disappeared by 32 weeks gestation. The possible role of altered neural development, acute exposure to alcohol and disruptions to the fetus's behavioural repertoire, in mediating these effects are discussed.