Will it harm my breastfeeding baby if I drink wine, beer, or spirits?
That depends on how much and when you drink the alcoholic beverage. Your blood alcohol levels (and the level of alcohol in your milk) will generally be highest one to one and a half hours after your last drink, although that time - and the length of time it takes the alcohol to dissipate from your body - varies from person to person.
The occasional glass of wine or celebratory cocktail doesn't appear to harm a nursing baby or interfere with milk production in the long run. One study found that babies who are exposed regularly (at least daily) to alcohol in their mother's milk during the first three months of life might have a slight but significant slowing of motor development, although another study found no such effect.
Studies do show that a baby drinks less milk if her mother has recently drunk alcohol. And drinking large amounts may make your baby drowsy or sluggish, which could interfere with her sucking ability. Drinking as little as one drink may also affect your milk letdown reflex (your breasts' natural ability to produce milk). And heavy drinking may impair your ability to care for your child. One study also found that babies slept for significantly shorter periods of time in a three and a half hour period after nursing if their mothers had had an alcoholic beverage.
If you're going to enjoy an occasional alcoholic beverage or have more than one drink, wait at least two hours per drink before nursing your baby to give the alcohol a chance to dissipate. One drink is considered 4 ounces of wine, one beer, or one mixed drink. Alcohol isn't stored in breast milk, so "pumping and dumping" (using a breast pump to empty your breasts and then throwing out the collected milk) serves no purpose. And be sure to down a nonalcoholic drink for every cocktail you quaff, to ward off dehydration. what's worse, feeding the baby formula or drinking more than 2-3 drinks a day while breastfeeding?
ETA If a woman you know who was bf was out drinking, would you advise her to give formula instead of bm that night?