A group of 156 predominantly white and middle-class pregnant women (mean age 26.5) were interviewed about their consumption of alcoholic beverages in the 6 mo. before pregnancy and in early (1st-4th mo.) and late (5th-8th mo.) pregnancy. Consumption was estimated from the absolute alcohol content of the typical quantities drunk per drinking occasion multiplied by the frequency of occasions. The average daily consumption before pregnancy was 0.34 oz; in both early and late pregnancy, 0.15 oz. The decrease in alcohol use during pregnancy was proportional to prepregnancy drinking levels. Of the 89 women who reported a decrease in their use of alcoholic beverages, 52% attributed the decline to an adverse physiological effect such as nausea, headache or the diuretic effect of alcohol, 38% reported that alcohol tasted or smelled bad or otherwise did not appeal to them and 36% cited concern for fetal welfare or other health considerations. Women who drank heavily before pregnancy reported a changed physiological reaction to alcohol during pregnancy more often than did the lighter drinkers. A decrease in the consumption of coffee was also reported during pregnancy, but the women who decreased their coffee intake were not necessarily those using less alcohol. Both alcohol and caffeine may be embryotoxins, and there might be biological regulation to avoid substances that may be noxious to the fetus.