Abstract

Potter defined congenital malformation as an “ abnormality of structure detected at birth or during first few weeks of life26 ”. It can be expanded to include functional disturbances in the organs. Congenital conditions can be referred to as diseases, defects, disorders, anomalies, or simply genetic differences. The usage overlaps, but also involves a valued judgement as to the harmfulness of the condition. Congenital malformations involving the brain are the largest group at 10 per 1000 live births, compared to heart at 8 per 1000, kidneys at 4 per 1000, and limbs at 1 per 1000. All other physical anomalies have a combined incidence of 6 per 1000 live births16. Congenital malformations of the heart have the highest risk of death in infancy, accounting for 28% of infant deaths due to birth defects, while chromosomal abnormalities and respiratory abnormalities each account for 15%, and brain malformations about 12%42. The cause of 40-60% of congenital physical anomalies (birth defects) in humans is unknown. These are referred to as sporadic birth defects, a term that implies an unknown cause, random occurrence, and a low recurrence risk for future children25. For 20-25% of anomalies there seems to be a "multifactorial" cause, meaning a complex interaction of multiple minor genetic abnormalities with environmental risk factors. Another 10-13% of anomalies have a purely environmental cause (e.g. infections, illness, or drug abuse in the mother). Only 12-25% of anomalies have a purely genetic cause. Of these, the majority are chromosomal abnormalities41. The rapid development of technology allowing early and accurate prenatal diagnosis of fetal disorder has revolutionised the practice of obstetrics over 20 years. Beginning with simple cytogenetics17 to detect chromosomal abnormality in amniotic fluid cells, there are new methods that permit rapid detection of mutant genes by using minute quantities of fetal DNA37. These techniques coupled with molecular genetics allow detection of a list of inherited conditions that is expanding8 almost daily. Of paramount importance is the ability to provide counselling regarding various screening, diagnostic technique and treatment options.

Description