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 300ml) or a single shot of spirits, while a small glass 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.

　　Vocabulary:

　　foetus：胎儿

　　midwife: 助产士