Drinking in moderation through pregnancy does not harm a baby’s neurodevelopment – but this could be because affluent mothers are more likely to do so, according to new research.

Children whose mothers consumed the equivalent of a glass of wine a day were able to balance as well as those who had not been exposed to alcohol in the womb.

Almost 7,000 10-year-olds were asked to take part in balance tests, which are an indicator of prenatal neurodevelopment.

The drinking habits of their mothers had been recorded during and after pregnancy, with those who drank three to seven glasses of alcohol a week classed as moderate drinkers.

Social advantage could be a large factor in the findings, as the research found mothers who were more affluent and better educated were more likely to drink in moderation.

Mothers from a working-class background were more likely to abstain from alcohol through pregnancy, to drink heavily or binge drink.

The study, which has been published by the journal BMJ Open, was led by John Macleod, from the University of Bristol’s School of Social and Community Medicine.

“Most of the women in this study either didn’t drink at all or if they did drink, they didn’t drink very much,” Macleod said.

“There weren’t many heavy drinkers. We know that heavy drinking during pregnancy has bad effects on a developing foetus.

“The moderate drinkers consumed an equivalent of up to one glass of wine a day.

“When we compared moderate drinkers with women who didn’t drink at all we actually found that in relation to a number of different tests of balance the children of moderate drinkers appeared to do better.

“However, we also found that the women who moderately drank compared to women who didn’t drink tended to be more middle class.

“They were more socially advantaged. Having a middle-class mum compared to having a working-class mum is likely to advance a child in a lot of ways.

“They may have better balance, they might do better at school. Having middle-class parents has advantages to a child that are nothing to do with alcohol.”

The 10-year-olds were part of the University of Bristol’s Avon Longitudinal Study of Parents and Children (Alspac).

Alspac has been tracking the long-term health of around 14,000 children born between 1991 and 1992 to women living in the former Avon region of the UK.

Children of women whose alcohol consumption was recorded during pregnancy, at 18 weeks, and after pregnancy, at 47 months, underwent a 20-minute balance assessment aged 10.

The assessment included a number of balance tests such as walking on a beam and standing on one leg for 20 seconds with eyes open and then closed.

Researchers also asked the children’s fathers how much alcohol they drank when their partners were three months pregnant.

More than half consumed one or more glasses per week, with one in five drinking one or more glasses a day.

In contrast, 70 per cent of the mothers drank no alcohol while pregnant. One in four drank between one and seven glasses a week.

Just 4.5 per cent drank seven or more glasses a week. Around one in seven of these mothers were classified as binge drinkers, consuming four or more glasses at once.

The mothers were also assessed four years after the pregnancy and 28 per cent said they did not drink at all, while over half consumed between three and more than seven glasses a week.

Higher total alcohol consumption by mothers before and after pregnancy – and fathers during the first three months of pregnancy – was associated with better performance for the children, particularly for static balance.

MacLeod said: “The way we investigated this further was to look at genes. People who carry a certain gene are for more likely not to drink alcohol on average.

“If it was really true that using a small amount of alcohol during pregnancy benefited children’s balance then we would expect those with mums who had the gene to have worse balance.

“We didn’t see any evidence that babies of mothers with this gene had worse outcomes than those who drank.

“There was a weak suggestion that children of mothers with the gene had better balance but our study was too small to show this reliably.”

He said that results showed that after taking account of influential factors such as age, smoking and previous motherhood, low to moderate alcohol consumption did not seem to interfere with balance.

But better balance was associated with greater levels of affluence and educational attainment.

MacLeod said: “In this group of mothers, moderate alcohol intake was a marker for social advantage which could be a key factor in better balance.

“It could possibly override subtle harmful effects of moderate alcohol use.

“The supposed benefits we saw are not the effects of alcohol, they are effects of middle classness.”

A spokesman for the UK Department of Health said: “Drinking during pregnancy can be associated with miscarriage, foetal alcohol syndrome and low birth weight.

“Our advice remains that women who are trying to conceive or are pregnant should avoid alcohol. If women choose to drink, to minimise the risk to the baby they should not drink more than one to two units of alcohol once or twice a week and should not get drunk.

“The Chief Medical Officer is overseeing a review of alcohol guidelines. This will include reviewing any new evidence on alcohol and pregnancy. To encourage mothers-to-be to cut out risky health behaviours like drinking alcohol we recently relaunched Start4Life.”