Any amount of alcohol, even one glass of wine, passes from the mother to the developing baby. Wine, beer, or distilled spirits (vodka, rum, tequila, etc.) all pose a risk.
Developing babies have the same blood alcohol concentration as their mother, but they lack the ability to process or metabolize alcohol.
The Institute of Medicine says, “Of all substances of abuse (including cocaine, heroin, and marijuana), alcohol produces by far the most serious neurobehavioral effects in the fetus.”