Experts are still unsure exactly how much – if any – alcohol is completely safe for you to have while you're pregnant, so the safest approach is not to drink at all while you're expecting.
Is it safe to drink alcohol when pregnant?
The Chief Medical Officers for the UK recommend that if you're pregnant or planning to become pregnant, the safest approach is not to drink alcohol at all to keep risks to your baby to a minimum.
Drinking in pregnancy can lead to long-term harm to the baby, with the more you drink, the greater the risk.
How does alcohol affect my unborn baby?
When you drink, alcohol passes from your blood through the placenta and to your baby.
A baby's liver is one of the last organs to develop and does not mature until the later stages of pregnancy.
Your baby cannot process alcohol as well as you can, and too much exposure to alcohol can seriously affect their development.
Drinking alcohol, especially in the first 3 months of pregnancy, increases the risk of miscarriage, premature birth and your baby having a low birthweight.
This is copied from NHS website. There is no confirmed safe amount of alcohol.