Previous research had suggested that a couple of glasses of wine a week was acceptable and would not damage the unborn child.
But now the Royal College of Obstetricians and Gynaecologists (RCOG) has said the only way to stay safe is to abstain completely from alcohol.
This is in keeping with the NICE guidelines, and with American policies, which recommends expectant mothers never drink during pregnancy.
Experts warn that the alcohol could be passed through the placenta, and that it can increase the chance of miscarriage.
6,000 babies a year in the UK are born with some kind of damage as a direct result of alcohol.