No amount of alcohol has been proved safe during pregnancy. To be safe, don't drink any alcohol.
Consider the risks. Drinking alcohol during pregnancy leads to a higher risk of miscarriage and stillbirth. Drinking alcohol also may result in fetal alcohol syndrome. The syndrome can cause the face to form oddly and cause lower intelligence.
If you're worried about alcohol you drank before you knew you were pregnant, or if you think you need help to stop drinking, talk to your health care professional.