Down's syndrome in Saudi Arabia: incidence and cytogenetics.

A study has been carried out in Riyadh to determine the incidence and distribution of Down's syndrome births during a 9-year period from July 1982 to June 1991. Down's syndrome was ascertained in 42 (23 females and 19 males) of 23,261 consecutive babies born alive to Saudi women, giving an incidence of 1 in 554 live births (1.8 per 1,000). A trend towards an increased incidence of Down's syndrome with advanced maternal age or increased maternal parity was found. Cytogenetic studies were performed on 37 cases of which all but 1 were non-disjunction trisomy 21, while the remaining infant had a translocation. This study provides the first step for further epidemiological surveys of Down's syndrome in the Kingdom of Saudi Arabia in order to prepare the ground for an effective antenatal screening programme for chromosomal disorders.