Global burden of genetic disease and the role of genetic screening.

It is estimated that 5.3% of newborns will suffer from a genetic disorder, when followed up until the age of 25 years. In developing, as compared to western countries, hemoglobinopathies and glucose-6-phosphate dehydrogenase deficiency have a higher incidence due to severe falciparum malaria in the distant past, and autosomal recessive disorders have a higher frequency due to greater proportion of consanguineous marriages. Chromosomal disorders have a combined frequency of 1 in 153 births, therefore screening for chromosomal disorders is essential, using biochemical markers, ultrasonography, and recently by non-invasive prenatal diagnosis based on cell-free fetal DNA in maternal plasma. Preconceptional counseling should be encouraged. For genetic disorders screening should be carried out, ideally after marriage, but before pregnancy. The disorders to be screened depend upon ethnicity. Metabolic disorders have a high incidence in developing countries due to greater rate of consanguineous marriages. Newborn screening is recommended to reduce the burden of these disorders, as many metabolic disorders can be treated. Hearing and critical congenital heart disease should both be screened in the newborn period.