Cystic fibrosis and fragile X syndrome: The arguments for antenatal screening

The ultimate public health aim of genetic screening is prevention. This can be achieved by reducing birth prevalence through primary or secondary meth ods such as pre-conceptional or antenatal screening. Tertiary prevention by neonatal screening is alsb an option where there is direct unbiased eviden ce for a substantial improvement in prognosis. In addition to this, the inf ormation provided during screening is also of value, enabling individuals t o make choices that otherwise would not have been available. Having elucida ted the natural histories and genetic defects underlying two common, seriou s genetic disorders, cystic fibrosis and fragile X syndrome, considerable e fforts have been channelled into ascertaining the most efficacious method o f prevention. To date there is only indirect evidence to suggest that neona tal screening improves prognosis in cystic fibrosis. Similarly, treatment f or fragile X syndrome is limited and therefore early identification of the disorder by neonatal screening is unlikely to improve long term outlook. Th us the focus of this review is on primary and secondary preventive methods.