While several rat studies indicate that alcohol is more toxic during adolescence than adulthood, some researchers believe that it remains unclear whether this is also the case in humans. Though heavy binge drinking adolescent humans show impaired brain activity during memory tests and underdeveloped brain structures compared to adolescents who did not binge-drink, they argue that these findings are similar to adult alcoholics who did not abuse alcohol during adolescence.  Extrapolation from animal studies to humans is notoriously difficult,  and a review by the group Choose Responsibility concluded that alcohol's long-term damage to cognitive processes was the same regardless of whether heavy drinking commenced during adolescence or later. 
In a study that included more than 365,000 participants since 1977, as reported in the journal Neuropsychiatric Disease and Treatment, moderate drinkers were 23 percent less likely to develop cognitive impairment or Alzheimer's disease and other forms of dementia. "Small amounts of alcohol might, in effect, make brain cells more fit. Alcohol in moderate amounts stresses cells and thus toughens them up to cope with major stresses down the road that could cause dementia," said Edward J. Neafsey, ., co-author of the study, as reported by Science Daily . "We don't recommend that nondrinkers start drinking," Neafsey said. "But moderate drinking — if it is truly moderate — can be beneficial."
I am so disappointed to see that Harvard Medical spreading information that could cause a lifetime brain damage to a fetus and jeopardizing international effort leaded by NIAAA! The study mentioned in the article is still unpublished and if it would be published it will get its harvest. Majority of studies around the World show us that we are severely underestimating this risk. Yes, there is chance to have a healthy looking baby and the rest of your lives wonder why he or she behaves so unsocial. And weather this kids could become Einstein, Curie or Mozart if only Mom was not surrounded by “kindly permissive” media and aggressive alcohol advertising.