Women who drink heavily while pregnant can cause severe damage to the foetus - but scientists may be closer to preventing it.
The developing foetus is vulnerable to the effects of alcohol
The finding - a body chemical which appears to protect brain cells from damage - could one day lead to drug treatments for pregnant alcohol abusers.
Foetal alcohol syndrome encompasses a number of problems that can aflict children born to women who drink heavily during pregnancy.
Consequences can include mental retardation and growth problems - FAS is the most common preventable cause of mental retardation in children.
It is caused by the toxic effects of alcohol on the brain cells of the foetus.
However, scientists at Harvard Medical School are unravelling a complex chemical process which may hold the key to preventing at least some of this damage.
They have examined how a protein called NAP - known to protect brain cells from a wide variety of toxins - works in the body.
Various strains of mice with subtle genetic variations were bred to try to examine exactly how NAP carries out the job.
One strain in particular appeared to lose its ability to protect against everything but alcohol - allowing scientists to look more closely at the anti-alcohol effect.
The result was a clue as to how ethanol in alcoholic drinks wreaks havoc in the developing nervous system of the foetus by preventing a key process from taking place.
Now scientists believe that if they can block this "inhibitory" effect of alcohol, they could prevent much of this developmental damage.
Writing in the journal Proceedings of the National Academy of Sciences, they said: "These findings...raise the possibility of identifying safe 'ethanol antagonists'."
Experts say that any drug in the future could help protect the unborn children of alcoholic women who simply cannot control their addiction, even though they are pregnant.