HEALTH / Second Opinion

AS EARLY as the eighth week in pregnancy - when a woman may still not have told her friends that she is having a baby - the embryo has developed its major organs. About one in 50 embryos has a defect in the heart, nervous system or limbs; faults in development occur in the crucial first few weeks. This proportion could be reduced but only one woman in 20 who becomes pregnant in Britain is taking all the preventive measures that are available.

One of the most common major defects is a fault in the development of the neural tube that forms the spinal cord and the brain. The severity of the defect (commonly known as spina bifida) varies from a lethal malformation of the brain to a minor abnormality of the bones of the lower spine. Twenty years ago 2,000 babies were born each year in Britain with partial paralysis and bowel and bladder problems. Surgery could help a little but most had permanent handicaps. The first step in reducing the numbers of babies born with these defects was the introduction of screening tests to allow their recognition at a stage when the pregnancy could be terminated. Screening has cut the numbers born to around 400 a year, but the tests are not routine in every hospital and some couples object to abortion in these circumstances.

Research indicated that nutrition in early pregnancy might be a crucial factor in causing spina bifida. A massive Medical Research Council study showed conclusively that a woman could dramatically reduce her risk of having a baby with spina bifida by taking the B vitamin folic acid for a month before conception and for the first 12 weeks of pregnancy. Folic acid is found in green leafy vegetables, beans, and wholemeal bread, but it is not yet clear whether women can get enough of the vitamin from these sources to give their babies maximum protection. The Expert Advisory Group on Folic Acid and Neural Tube Defects recommends that women at high risk - those who have had an affected baby in the past or whose relatives have had an affected baby - should take 5mg of folic acid daily in tablet form and that all other women planning pregnancy should take a lower dose (0.4mg).

Recent studies reported in the Lancet have shown that only 2-3 per cent of women attending antenatal clinics had taken folic acid supplements in the crucial 'periconceptual' weeks just before and just after conception of the baby. At least one third of babies are the result of unplanned pregnancies, and in these circumstances preventive treatment may be difficult. Taking folic acid is one precaution; there is also some persuasive evidence that abstention from alcohol is important, and women who have diabetes need to control their blood sugar levels.

Most women starting a family do not go to their doctors until they have missed a period, maybe two. By that time it is too late to take folic acid to prevent spina bifida. Some experts suggest that all women who might become pregnant should be taking the vitamin, but that assumes that they are aware of the benefits and are prepared to buy the tablets. Free supplies might help, but the real problem is getting the message across to women who have never heard of the disorder let alone its prevention.