Sex ratio of children with trisomy 21 or Down syndrome.

In a sample of 75 children with trisomy for chromosome 21, or Down syndrome, there were 42 males and 33 females. The sex ratio was 1.30 which is statistically not significant (p greater than 0.05). However, a similar sex ratio (1.36) was reported in a larger sample size which was statistically significant (p less than 0.01). This discrepancy was due to the size of the samples. The two studies suggested an excess of males in the referred population. The decreasing age of mothers of infants with Down syndrome was also evident. Furthermore, more, more males with Down syndrome were born to young couples (age less than 35 years) while elderly couples had an excess of girls.