The official recommendation in the United States starting with the surgeon general and continuing with medical organizations is that you should not have any alcohol during pregnancy. Women who are pregnant, those planning a pregnancy, or women at risk for pregnancy are advised to not drink any alcohol.
In the UK however, recommendations are different: The current UK Department of Health guidelines recommend that women who are trying to become pregnant or are at any stage of pregnancy should not drink more than 1 or 2 units of alcohol once or twice a week and should avoid episodes of intoxication.
Alcohol is the #1 drug responsible for fetal malformations. Here is what the Centers for Diseases Control (CDC) say about Alcohol Use During Pregnancy:
"Because no safe threshold of alcohol use during pregnancy has been established, CDC and NTFFAS/FAE recommend that the following women should NOT drink alcohol:
- Women who are pregnant
- Women planning a pregnancy
- Women at risk for pregnancy
Women of childbearing age who are not pregnant or planning to get pregnant should drink no more than seven drinks per week and no more than three drinks on any one occasion."
With this recommendation in mind, there are now enough studies that show that small amounts of alcohol in pregnancy are unlikely to bring harm to the fetus.
The authors of this study said: "This systematic review found no convincing evidence of adverse effects of prenatal alcohol exposure at low-moderate levels of exposure. However, weaknesses in the evidence preclude the conclusion that drinking at these levels during pregnancy is safe."
What is a small amount? Probably 1-2 units of alcohol once or twice a week are considered to not increase fetal risks.
But when in doubt, and because alcohol is not an essential part of your daily nutrition, you are still safest to stay away from alcohol.