Not enough is known about foetal alcohol spectrum disorder (FASD), a condition that is often misdiagnosed or missed completely, charities say.
The main symptoms of FASD include growth problems, behavioural issues, learning difficulties and issues with hearing or eyesight.
There is no treatment for the condition but its symptoms can be managed.
When Anna Webster adopted her son, she was told his birth mother had drunk alcohol during her pregnancy but she had no idea of the effect it would have on him.
“He was a lovely, gorgeous little baby,” she told Sky News.
“There weren’t any obvious signs particularly, but he was always very hyper, had lots of energy and had some difficulty with focusing and concentrating and speech and language issues as well.”
Because so many cases are not picked up – with some people being labelled as badly behaved, for example, it is difficult to know exactly how many people are suffering with the condition.
Sandra Butcher from the charity NOFAS-UK, which is raising awareness of the condition, told Sky News: “A conservative estimate would be more than two percent of the population, so here in England that translates into more than 15,000 babies a year.
“It’s vastly undiagnosed and it’s something that the government is going to have to really get on top of because the problem is that these children are being seen in the NHS through different services but they’re not being properly supported so it’s kind of a waste of resources.”
Dr Raja Mukherjee works at a clinic specialising in the disorder in Surrey and cites research showing there are serious consequences for adults who have not been diagnosed.
“If you don’t support it then 90% have gone on to have mental health problems, half the group that they were studying ended up in prison at some point, a third of them ended up with their own addictions,” he said.
“There are lots of secondary disabilities. Many of them end up homeless or on social security so there’s a lot of support that’s needed.”
On International FASD Awareness Day (9 September), charities are calling for more help and advice for vulnerable mothers.
Adoption UK described the situation as a “hidden epidemic”.
John Simmonds from CoramBAAF adoption and fostering academy told Sky News: “Children who come into care, whether they then go on to be adopted or into foster care, are likely to come from a group of families who face all kinds of adversities but where alcohol and drug use are quite common.”
A Department of Health and Social Care spokesperson said: “The chief medical officer’s low risk drinking guidelines provide clear advice for women across the UK that for those who are pregnant, or could become pregnant, the safest approach is not to drink alcohol at all.
“However, we know that more needs to be done for vulnerable groups and later this month, we will be hosting an expert roundtable on foetal alcohol spectrum disorder to inform the new alcohol strategy.”