The authority, which issues guidelines to medical staff and patients across the UK, made the announcement yesterday after issuing previous advice that mothers-to-be could safely drink 1.5 units of alcohol a day, equivalent to a small glass of wine, after the first three months when the risk of miscarriage decreases.

Kate Edmondson, who is a press officer with Northamptonshire County Council and is expecting her second child next month, said the advice added to an already confusing situation.

The 30-year-old said: "I'm more confused than I've ever been. I've still got a couple of books from my first pregnancy and I looked back on them only last night. One said no more than 10 units per week, the other said two. NICE previously said two units and then Tommy's the baby charity advised between five and seven after the first three months.

"I would like to see more evidence on the effects of alcohol on the unborn baby but it is a difficult one to find evidence for. What would be good is if there could be one guideline issued for everything, rather than all this conflicting advice."

Helen Killeya, who runs Bumps and Babies Teastop, a breastfeeding cafe at the Sure Start Camrose Centre Community Room, Tenby Road, Northampton, agreed the situation was extremely confusing.

She said: "I've got pregnant nieces and I know how confusing it is for them. There is a lot of guilt involved and if something does go wrong then people are more likely to blame themselves. Instead of accepting that's the way things are they will think they did something wrong."

GP David Smart, who works at Leicester Terrace Health Centre in Northampton town centre, said simply because the advice offered to mothers was so confusing, he would tell pregnant women not to drink alcohol at all.

He said: "It is best to avoid alcohol. I think one review suggested women could drink in moderation, and then someone else said they shouldn't and because of the confusion there needed to be a single plan. There's certainly a foetal alcohol syndrome problem and that's something that needs to be thought of quite seriously."

Foetal alcohol syndrome can leave children with impaired IQ and low birth weight, leading to severe learning difficulties and addiction problems in adulthood. But Dr Smart said it was unclear precisely how much alcohol would be consumed to trigger the condition.

He said: "Alcohol can cause problems, it is a drug and I think people forget that. It does cause harm so at the moment the guidance is right, there is no safe limit."