Government advisers are to consider increasing genetic screening programmes for pregnant women to reduce the number of babies born with inherited learning disorders.
Researchers commissioned by the NHS have recommended trials of tests for an inherited condition called fragile X syndrome. Lifelong state-funded care can be needed for people with the condition, especially for boys.
They conclude that even the most expensive option - a screening programme for all pregnant women rather than just those at high risk - would be "acceptable" and "cost-effective", assuming most mothers with a positive result terminated their pregnancy.
About 10,000 people in England and Wales are thought to have fragile X syndrome, with varying degrees of severity.
A subgroup of the national screening committee, which advises on such programmes, is to consider the report on October 13. It says such screening would be introduced only as part of an ethically approved research project.
The trials are sure to raise new questions about the ethics of medical abortions.
Increased debate had already been expected because from 2004 the government intends to allow all mothers-to-be to find out whether their baby has Down's syndrome, caused by a chromosomal abnormality and found in about one in 1,000 births. At the moment about 80% of women are offered first screening.
Most people with Down's live fulfilling lives, many attending mainstream schools. Life expectancy is around 60.
According to the NHS researchers, led by Fujian Song of Birmingham University, fragile X syndrome is found in about one in 4,000 boys and one in 8,000 girls, although some say it is more widespread. It is the most common inherited condition involving a learning disorder.
It is incurable and generally more severe than Down's, although there are people who could survive in mainstream education with support.
Lesley Walker, founder of the Fragile X Society, said affected families already had to make choices: whether to have children at all, whether to opt for IVF or instead to try for a natural pregnancy and risk passing on the condition.
Families, she said "all feel very differently about it" and the screening debate must be handled very sensitively.
Mrs Walker is seeking residential care for her son Andrew, 18, who has the condition, while his twin Clare, who does not, is going to university this year.
The Birmingham study, conducted under the NHS's health technology assessment programme, involved a review of previous research and economic calculations.
