After spending 5 days in Sin City, where alcohol is abundant, I wanted to report on the effects of alcohol on breastfeeding. Alcohol, like most medications, does enter BM, but most research and publications on the issue say light, occasional drinking while BF is ok (think 1-2 drinks of the light stuff a week, e.g. a glass of wine or beer).
According to the AAP, moderate or excessive amounts of alcohol will affect both Mom and baby. For Mom, alcohol can interfere with the let-down reflex, and for baby, it can cause drowsiness, slow weight gain and decrease motor development, among other things.
Some articles recommend if you are going to drink alcohol, avoid nursing for 2-3 hours afterwards. But the best advice of all is to use common sense. BF Mom's obviously want to give their babies the best, so when in doubt, skip the sauce!