NTD are birth defects of the brain or spinal cord caused by abnormal neural-tube development (the neural tube being the origin of the brain and spinal cord) in early pregnancy; anencephaly (partial or complete absence of the brain) and spina bifida are the most severe NTD which cause serious physical and mental impairment. Abnormal metabolism of folic acid is an established risk factor for NTD; it has also been implicated as a possible risk factor for trisomy 21 (the chromosomal abnormality which causes Down's syndrome).
A collaborative research group from the Ukraine (Svetlana Arbuzova), Israel ( Gad Barkai) and the UK (Howard Cuckle) investigated whether Down's syndrome and NTD arise more often in the same family than would be expected from the incidence of each disorder considered separately. Two types of families were studied: 493 families from Israel who were at high risk of NTD, and 516 families from the Ukraine at high risk of Down's syndrome.
There were more than 5 times the number of pregnancies affected by Down's syndrome (11 in total) in 1492 pregnancies in families with a high risk of NTD compared with 1.87 expected for women of the same age; there was a similar ratio of increased NTD in the families at risk of Down's syndrome (seven compared with an expected incidence of 1.37) among 1847 pregnancies.
Howard Cuckle comments: "This study provides direct evidence of a link between Down's syndrome and NTD. Folate supplementation before conception has the potential to reduce the frequency of Down's syndrome."
In an accompanying Commentary (p 1316), Jørgen Olsen and Jeanette Falck Winther state that some biases in the study will need addressing in future research before folic-acid supplementation can be recommended to help prevent Down's syndrome in the general population. They comment: "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."
Contact: Professor Howard S Cuckle, Reproductive Epidemiology, Leeds Antenatal Screening Service/International Downs Syndrome Screening Group, 3 Gemini Park, Sheepscar Way, LEEDS LS7 2JB, UK;
T) 44-113-284-9233 ;
M) 44-794-687-3342;
F) 44-113-262-1658;
E) h.s.cuckle@leeds.ac.uk
Dr Jørgen Olsen, Institute of Cancer Epidemiology, Danish Cancer Society, DK-2100Copenhagen, Denmark;
T) 45-3525-7654;
F) 45-3525-7734;
E) jorgen@cancer.dk
Journal
The Lancet