A supplement may change the biochemistry of brain fluid
Researchers say taking a special vitamin supplement during pregnancy could prevent hydrocephalus - one of the most common birth brain defects.
Tests on rats showed a combination of folates dramatically reduced the rates of hydrocephalus - in which fluids build up in the brain's chambers.
They even seemed to work after the condition had started to develop.
But the work, published in the Journal of Neuropathology and Experimental Neurology, is still at an early stage.
Excessive accumulation of cerebrospinal fluid in the cavities of the brain
Puts a harmful amount of pressure on tissues in the brain
Most obvious symptom is an unusually large head size. Other symptoms can include: vomiting, sleepiness, irritability, downward deviation of the eyes and seizures
Many children also display symptoms that can be mistaken for naughtiness, such as verbal aggression and swearing, hyperactivity, not paying attention and generally unusual behaviour
They may also experience learning difficulties at school
The team from the universities of Manchester and Lancaster hope to get permission to start clinical trials in pregnant women with babies diagnosed with hydrocephalus.
The supplement itself is not currently available, so they are also seeking the support of a pharmaceutical company willing to produce it as a pill.
At present hydrocephalus affects one in 1,000 live births. There is no satisfactory treatment for it other than surgical diversion of the fluid through a tube, known as a shunt, from the brain to the abdomen or heart.
However, shunts are permanent and prone to infection and blockage, which means patients may require several operations during their lifetime.
Most of those with by the condition have impaired mental and physical ability, although the effects can vary widely.
The team also say they have shown it is the chemical composition of cerebrospinal fluid - rather than the fluid itself putting pressure on the brain - which causes the problems.
Lead researcher Jaleel Miyan said: "Cerebrospinal fluid is not a liquid which simply cushions the brain and carries chemicals around it. It is actively produced and transported and plays an essential biological role in developing the brain".
The combination of supplements appeared to stimulate this process.
At present women are advised to take folic acid - a synthetic substance found to prevent spina bifida - but this does not appear to promote brain cell growth in the same way as the combination.
Andrew Russell, head of the Association for Spina Bifida and Hydrocephalus, said: "Hydrocephalus can cause severe disability and learning difficulties, so the possibility of prevention through a specific vitamin supplement is exciting.
"ASBAH is helping with this ground-breaking research because many babies born with hydrocephalus today survive, but with a lifelong disability.
"However, a lot of further work is still needed to prove this approach is effective, through clinical trials.
Dr Imogen Montague, a spokeswoman for the Royal College of Obstetricians and Gynaecologists, said the study was "potentially very exciting".
"There are so few things we can currently do to decrease the incidence of birth defects so these findings are really to be welcomed.
"But we do have to be cautious about the results - extrapolating results from rats may be problematic, and we need to know both whether it works, and whether it is safe for use in humans. Any general use would still be a long way off."