It’s good that you have breast milk frozen. Make sure you have as much frozen as possible. Dumping and wasting once thru the night is a good idea simply so your breasts don’t become impacted and sore. I think that by the time you are no longer feeling the effects of the alcohol, it should be out of your breast milk. But depending on how much you drink, the timing can be much longer.

So if it were me, I’d pump enough ahead of time to get the baby through the night and then some. Have more breastmilk saved than you might think is necessary because you never know, as the evening progresses, you may be out longer than you plan or you may have a drink later than the planned stopping time or more to drink altogether than you plan.

It takes approximately 3 to 4 hours for the alcohol from one drink to leave your breastmilk. So you need to keep this in mind when deciding how much alcohol to drink. The more you drink, the longer it will take for the alcohol to leave your breastmilk. I know it’s your 21st birthday, but you may want to still drink in moderation.

Here’s a reputable site with good information; it’s the La Leche League.

http://www.llli.org/FAQ/alcohol.html