Prenatal alcohol exposure is the cause of fetal alcohol syndrome. A study of over 400,000 American women, all of whom had consumed alcohol during pregnancy, concluded that consumption of 15 drinks or more per week was associated with a reduction in birth weight. Though consumption of less than 15 drinks per week was not proven to cause FAS-related effects, the study authors recommend limiting consumption to no more than one standard drink per day. Also, threshold values are based upon group averages, and it is not appropriate to conclude that exposure below this threshold is necessarily ‘safe’ because of the significant individual variations in alcohol pharmacokinetics.
An analysis of seven medical research studies involving over 130,000 pregnancies found that consuming two to 14 drinks per week did not significantly increase the risk of giving birth to a child with either malformations or fetal alcohol syndrome. Pregnant women who consume approximately 18 drinks per day have a 30-33% chance of having a baby with FAS.
A number of studies have shown that light drinking (1-2 drinks/week) during pregnancy does not appear to pose a risk to the fetus. A study of pregnancies in eight European countries found that consuming no more than one drink per day did not appear to have any effect on fetal growth.
A follow-up of children at 18 months of age found that those from women who drank during pregnancy, even two drinks per day, scored higher in several areas of development, though in a different study, as little as one drink per day resulted in poorer spelling and reading abilities at age 6 and a linear dose-response relationship was seen between prenatal alcohol exposure and poorer arithmetic scores at the same age.