An experiment in mice has raised hopes of halting some of the effects of Down's syndrome before birth, New Scientist magazine reports.
Down's starves developing nerve cells of two key proteins, leading to problems with mental development.
But when US researchers injected the proteins into mice pregnant with "Down's" pups, the offspring seemed free of these problems.
However, experts warned success in mice was no guarantee of the same in humans.
Down's syndrome in humans is caused in children who inherit an extra copy of one of the body's chromosomes - bundles of genetic material which help control how we develop and live.
Children with Down's can suffer from higher rates of heart and developmental problems, as well as learning difficulties to different degrees.
Statistics in the UK suggest that more children than in recent years are being born with the condition, with some parents encouraged by the fact that life expectancy is higher than in previous decades.
However, the research carried out at the National Institute of Health in Bethesda, Maryland, hints at the possibility of preventing some of the damage the extra chromosome causes.
One of the problems detected by earlier research is a malfunction in a type of brain cell which causes them to produce less of two proteins - NAP and SAL.
Normally these body chemicals help regulate the development of nerve cells.
The US researchers used mice pregnant with pups who also had a extra copy of a segment of one of their chromosomes.
These pups also show signs of developmental delay in their early months.
The mothers were injected with NAP and SAL, and when the pups were born, the speed with which they reached their "developmental milestones" - such as grasping a rod, righting themselves and responding to touch - matched that of normal mice.
The brains of the treated mice showed normal levels of another protein which is under-produced by Down's-affected brain cells.
The US team published its findings in the journal Obstetrics and Gynaecology, and is now following the mice further into childhood to see if the effects are long-lasting, or even permanent.
However, other US experts warned that experiments in mice did not necessarily mean that the treatment would be effective in humans.
Carol Boys, the chief executive of the Down's Syndrome Association, said: "We welcome research that may have a positive impact on people with Down's syndrome.
"However, it must be recognised that this research doesn't herald a 'cure' or 'treatment' for Down's syndrome. We'll be following how it develops with great interest."