The amount of alcohol in breast milk depends on the amount of alcohol in the blood. It takes about 2 to 3 hours after consuming one drink for the alcohol to be metabolized and no longer be a concern for nursing.
If you do plan to drink more than a few (preferably after breastfeeding's been established for about a month), you can "pump and dump" — pump your milk and then throw it away. Do not give your baby breast milk, from your breast or a bottle, for at least 2 to 3 hours for every drink of alcohol you consumed.
Alcohol consumption for pregnant and breastfeeding moms is not advisable. This can cause harm to your baby. Pregnant women and those who just gave birth must avoid alcohol and most especially drugs. It's very advisable to undergo alcohol treatment and drug treatment for those who are suffering from alcohol and drug dependence. There are special facilities like drug rehab and alcohol rehab which help people recover and learn how to turn away from their vices.
For the sake of the baby, mommies better avoid alcohol. There is an alcohol treatment center for those who want to make a difference.