Another thing that you should watch out for, according to La Leche League International, is your baby’s age. A 2-month-old baby, for example, has very limited liver function and would process alcohol at about half the rate of an adult
This means that even a small amount of alcohol could tax the baby’s liver. At around 3 months of age, however, an infant would process alcohol more quickly, more similar to an adult’s liver.
All that said, know that as long as you aren’t sucking down Jell-O shots and then nursing your baby, the occasional beer with your pizza or glass of wine with your bubble bath doesn’t have to be avoided like the plague.
However, nursing while you are drunk or frequently nursing when you’ve been drinking are problems. But, according to experts like Dr. Jack Newman, author of “The Ultimate Breastfeeding Book of Answers,” "Reasonable alcohol intake should not be discouraged at all … Prohibiting alcohol is another way we make life unnecessarily restrictive for nursing mothers.