A survey of chromosome anomalies in Malta

433 individuals referred for chromosome analysis between 1983 and 1987 were included in the survey. Among individuals with dysmorphic features or congenital anomalies 42% of babies referred in the neonatal period and 12 to 30% of individuals in older age groups had a chromosome abnormality. Chromosome abnormalities were also found in 10 or 11% of boys or girls with problems of pubertal development, in 14% of azoospermic or severely oligospermic men, in 8.3% of couples with repeated foetal loss and in 5% of couples with malformed children. Whereas most cases of autosomal aneuploidies were diagnosed, a large proportion of sex chromosome anomalies, particularly in males, remained undetected presumably because of under-referral in the pubertal period. The prevalence of chromosome anomalies in Malta was 2.20 per 1,000 births between 1984 and 1987. The incidence of Down Syndrome showed great annual fluctuation with a mean of 1.88 per 1,000 births of which 61% occurred in mothers over 35 years of age. The lowest occurrence risk for trisomy 21 appears to be in the 25 to 34 years maternal age group.peer-reviewe