Many women complain that while pregnant, their bodies becomes public property.

Complete strangers suddenly feel compelled to comment on how big they look, whether or not they should breast feed or might even give their bellies a pat.

Most of this advice is well-meaning, but some, as Caroline Williams discovered, can feel distinctly judgmental.

Ms Williams, who is 23 weeks pregnant, was asked to leave a pub after drinking a pint of lager. The barmaid objected when Ms Williams friend attempted to buy her another half pint and, when the 26-year-old sipped from a friend’s drink, she was told to leave.

The pub, the Sussex Cricketers on Eaton Road, Hove, has since issued an apology for its actions but it raises the question whether it is safe for women to drink alcohol while pregnant.

The official Government line is clear mums-to-be, and women trying to conceive, are advised not to consume any alcohol. But, as with much of the advice given during pregnancy, the guidance isn’t set in stone.

Many grandparents are baffled by the lists of what their daughters can’t eat or drink during their 21st century pregnancies.

Forty years ago, women were advised to smoke for a small baby and a bottle of Guinness was thought to boost iron levels.

But a visit to the NHS Direct website gives a taste of today’s banned substances. Pâté, coleslaw and soft cheese are all best avoided, as are swordfish and marlin ( which contain high levels of mercury) .

A quick look online finds women wondering whether to avoid Mr Whippy ice creams and peanut butter, because of listeria and allergy risks.

Just two years ago, the Government advised one or two units of alcohol, a small glass of wine or a half pint of medium strength lager, was fine for pregnant women to drink.

Dr Tom Scanlon, director of public health for Brighton and Hove City PCT, advises complete abstinence but acknowledges there is nothing to suggest a small amount of alcohol does any harm: “The science on this is not certain.

“Alcohol passes through the placenta but on the one hand there is no current evidence that the old advice about drinking one to two units a week during pregnancy had any adverse effect on the baby’s health.

“On the other hand the absolute safe levels of alcohol consumption during pregnancy are not clearly defined so we don’t know with certainty what is a safe level.”

He said the current advice reduced the risk of women saving up units and binge drinking while pregnant.

“The new guidance avoids any confusion. In theory, a women could binge drink once or twice during pregnancy but say that on average it came out to a couple of units a week, it’s unlikely I know, but it is possible.

“We do know that binge drinking has an adverse effect on the health of the baby. It is also estimated that about 6,000 babies are born with adverse effects from alcohol.

“So the line is really that it is safer not to drink anything. I would not like women to feel awful if they had a drink in line with the old guidance but neither would I be inclined to recommend it.”

Although the effect of moderate drinking is unclear, the effects of heavy drinking during pregnancy can be catastrophic for the baby.

Foetal Alcohol Syndrome is caused by women drinking during pregnancy. Babies suffering from the condition are born underweight and have slack muscle tone. They are born with brain damage and can suffer a range of problems including behavioural problems, heart and eye disorders and speech impediments.

The National Childbirth Trust, the UK’s largest parenting charity, takes a line similar to Dr Scanlon’s. It suggests cutting out alcohol completely or to no more than a couple of units a week.

It states: “We would suggest expectant mums follow the Department of Health advice to avoid alcohol completely or to cut down to one or two units of alcohol once or twice a week while pregnant.

“However, it’s important to put things into perspective. Pregnant women who have had a few drinks often worry a great deal about whether they have harmed their baby.

“On balance, for instance, it is believed that if a light, infrequent drinker, in general good health, drinks to the point of drunkenness on one occasion, the risk to her baby is small.”