Folic acid, a supplement taken by women trying to become pregnant to prevent spina bifida in their babies, may also help cut the risk of Down's syndrome.

Folic acid, a supplement taken by women trying to become pregnant to prevent spina bifida in their babies, may also help cut the risk of Down's syndrome.

An international study of 1,000 families has found that those at high risk of having a baby affected by spina bifida, a congenital disorder in which the spine is incompletely formed, were also at high risk of Down's syndrome, suggesting a link between the two disorders.

Spina bifida and Down's syndrome are among the commonest congenital malformations. Abnormal metabolism of folic acid – the essential mineral contained in green "foliage" such as spinach – is known to be a risk factor for spina bifida and related neural tube defects – defects of the tube containing the spinal cord.

It has also been implicated in preliminary research as a risk factor for the chromosomal abnormality that causes Down's syndrome. The new study adds to the evidence for the protective role of folic acid in this condition.

The research team from the Ukraine, Israel and the UK set out to examine whether spina bifida and Down's occur more often in the same family than would be expected from the incidence of each disorder considered separately.

They studied 493 families from Israel with a history of spina bifida and 516 families from the Ukraine with a history of Down's. The results, published in The Lancet, show that the incidence of Down's was five times higher than expected among the families at high risk of spina bifida with 11 cases among 1,492 pregnancies. There was a similar five-fold increased risk of spina bifida among the families at high risk of Down's.

Howard Cuckle, professor of reproductive epidemiology at the antenatal screening service in Leeds, said: "This study provides direct evidence of a link between Down's syndrome and neural tube defects. Folate supplementation before conception has the potential to reduce the frequency of Down's syndrome."

The authors say that investigating some mothers of Down's syndrome children has revealed abnormalities in their metabolism of folate. Theoretical analysis suggested that Down's and spina bifida could have a common cause, linked to folate metabolism, which would result in the two conditions occurring in families together than in the general population. Their study set out to test this theory and found it to be true.

A daily dose of 5mg of folic acid might be needed to reduce the risk of Down's syndrome, they say. A multi-centre trial is underway in which folic acid supplements are being given to mothers at high risk of Down's.

However, other experts urge caution in interpreting results. Jorgen Olsen and Jeanette Winther, of the Institute of Cancer Epidemiology in Copenhagen, say in a commentary that further research to confirm the findings is necessary before folate supplementation can be recommended to help prevent Down's syndrome in the general population.

They say: "Nevertheless, although the report is somewhat provocative, it may well be the first epidemiological indication of the existence of a mechanism which could be used at a later stage in the primary prevention of Down's syndrome.

¿ Noisy homes could be putting the mental development of babies at risk. New research indicates that constant background noise may swamp an infant's brain, holding back its ability to recognise sounds.The findings from the University of California at San Francisco might explain why language learning disorders have increased over the past few decades, it is claimed.

Modern homes are often filled with a cacophony of noise from blaring TVs and radios, to the rumble of traffic, jets flying overhead, as well as domestic machinery such as washing machines and fridges.