Prevention and avoidance of congenital malformations

Many congenital abnormalities do not have either a Mendelian pattern of inheritance or an identifiable chromosome abnormality and are described as 'multifactorial' as it is assumed they are determined by several genes, each with added effects and modified to a greater or lesser extent by environmental factors. They include spina bifida and anencephaly, cleft lip or cleft palate or both, congenital heart defect and congenital dislocation of the hip, and they constitute a major community health problem. Developments in genetics, biochemistry and cytogenetics have presented new approaches to the prevention and avoidance of congenital abnormalities. The approaches available for the avoidance of congenital malformations include the avoidance of harmful environmental factors, the screening of the newborn and early treatment, genetic counselling and antenatal monitoring with selective termination. The prevention of neural-tube defects in 'high risk' mothers can be achieved by periconceptional vitamin supplementation. In Northern Ireland, of 438 fully supplemented women, only 4 (0.98%) infants or fetuses among 407 infants and fetuses examined had a neural-tube defect, whereas of 356 unsupplemented women, 16 (4.7%) infants or fetuses among 337 infants or fetuses examined had a neural-tube defect.