ABC of clinical genetics. Chromosomal disorders II.

Developmental delay in child with deletion of chromosome 13. Chromosomal abnormalities are generally associated with multiple congenital malformations and mental retardation. Children with more than one physical abnormality, particularly if retarded, should therefore undergo chromosomal analysis as part of their investigation. Chromosomal disorders are incurable but can be reliably detected by prenatal diagnostic techniques. Amniocentesis or chorionic villus sampling should be offered to women whose pregnancies are at increased risk-namely, women in their mid to late thirties, couples with an affected child, and couples in whom one partner carries a balanced translocation. Unfortunately, when there is no history of previous abnormality the risk in many affected pregnancies cannot be predicted beforehand.