Ethanol and acetaldehyde concentrations in pregnant rats after administration of ethanol

Concentrations of ethanol and acetaldehyde in 20- day pregnant rats were determined following administration of ethanol. A single dose of 2 g ethanol/kg body weight was given via stomach tube and a rat was sacrificed every hour for 8 hours. In both the blood and livers of mother and fetus ethanol, concentrations were maximal at 2 hrs after administration, and the ethanol concentration-time curves were virtually identical during the 8 hrs. There was a time lag in the appearance of ethanol in the amniotic fluid, as compared with the appearance in the maternal and fetal blood and liver. Also, the ethanol concentration in the amniotic fluid was higher than that in the maternal and fetal blood during hours 4 to 8. Acetaldehyde was found in maternal blood, fetal blood, and amniotic fluid at concentrations at least 1000-fold lower than the ethanol concentrations, and was variable. For each biological fluid the acetaldehyde and ethanol concentration-time curves were not parallel. The acetaldehyde concentration in the maternal blood was about 10-fold greater than in the fetal blood. These data indicate that ethanol administered to pregnant rats undergoes unimpeded bidirectional placental transfer between the mother and fetus and that the amniotic fluid may serve as a reservoir for ethanol in utero.