Women should drink no alcohol during the first three months of pregnancy, despite uncertainty over whether the odd drink could harm their baby, a government watchdog said on Wednesday.
The National Institute for Health and Clinical Excellence (NICE) said there was limited evidence that drinking in the early stages of pregnancy may be linked to a higher risk of miscarriage.
Its new guidance says that pregnant women who choose to drink should limit their intake to one or two units, once or twice a week.
One unit equals half a pint of beer or a single shot of spirits, while a small glass (125 ml) of wine has 1.5 units.
While it is generally agreed that pregnant women should not drink to excess, studies have failed to find the exact level at which moderate alcohol consumption harms the foetus, the watchdog said.
"Doctors and midwives should advise women to avoid drinking alcohol when trying to get pregnant and during the first three months of pregnancy because there may be an increased risk of miscarriage," said NICE Deputy Chief Executive Dr Gillian Leng.
"If they do choose to drink alcohol while pregnant, women should also be advised to drink no more than one to two UK units once or twice a week."
In a statement, NICE said: "There is uncertainty about how much alcohol is safe to drink in pregnancy, but at this low level there is no evidence of any harm to their unborn baby."
The watchdog found "limited, poor-quality" evidence that alcohol may be linked to a higher miscarriage rate. A similar standard of evidence linked binge drinking with possible brain development problems.
The watchdog said it was hard to measure the effects of alcohol. Factors such as smoking and socio-economic status can confuse results. It is also difficult to measure accurately how much women drink.
Between a quarter and half of European women continue to drink during their pregnancy, it added.
The Department of Health and the Royal College of Obstetricians and Gynaecologists (RCOG) say the safest option is to avoid alcohol altogether.
"Women should also avoid getting drunk and binge drinking at any stage of their pregnancy," the RCOG said in a statement.
