Why do American blacks have fewer Down's syndrome births than any other racial group? And why should Hispanics fare the worst, with 11.8 Down's syndrome babies out of every 10,000 births?
A recent study, which tracked births in 17 states across the US between 1993 and 1990, discovered that the average incidence of Down's births among black people was 7.3 per 10,000, and 9.2 among whites. It also varied markedly between states, with 5.9 per 10,000 recorded in Kansas and 12.3 in Colorado.
One theory for the differences in the racial groups, put forward by the medical monitoring service Journal Watch, was that diagnostic services and abortions varied between them.
However, one conclusion not considered was environmental factors such as general radiation exposure or the use of x-rays, which may also differ between groups. Radiation was recently linked with a greater incidence of Down's syndrome after the Chernobyl nuclear accident (see
WDDTY, vol 5, no 6). Morbidity and Mortality Weekly Report, 26 August 1994.
Serum screening for Down's syndrome is offered by virtually every obstetrician in England and Wales yet 80 per cent of the women offered the test did not understand it. A questionnaire to doctors revealed the high level of misunderstanding among expectant mothers, and the lack of resource to counsel them.
!ABMJ, 24 September 1994.