Cytogenetic prenatal diagnosis and its relative effectiveness in the Mersey Region and North Wales.

The relative effectiveness of cytogenetic prenatal diagnosis in the Mersey Region and North Wales is presented by estimating the percentage detection rates of Down's syndrome annually following amniocentesis from 1978-1984 inclusive. Tables indicating the percentage of screened pregnancies, types of chromosomal aberrations detected and the occurrence of Down's syndrome in mothers in age groups of five-year intervals are also presented. The average prenatal detection rate for Down's syndrome (estimated at the time of birth) was 15.15 per cent over the years 1978-1984 and was above 22 per cent for the last two years when 44.13 per cent of all pregnancies to mothers of 35 years and over were investigated.