To the Editor.
—In the June 1991 issue of the Archives,1 Dr Flynn responded to a question about an association between retinopathy of prematurity and Down syndrome based on the notion that individuals with Down syndrome may have altered superoxide dismutase activity and, therefore, be more susceptible to oxygen or free radical injury.Dr Flynn correctly comments about elevated levels of superoxide dismutase in Down syndrome and also notes the absence of reported cases of retinopathy of prematurity among infants with Down syndrome. However, he reports that "Down syndrome occurs once in every 4000 to 5000 live births...." Even with the advent of prenatal testing and selective termination of pregnancy for Down syndrome, the incidence in most epidemiologic studies remains between one per 700 to one per 1000 live births, with the occurrence of trisomy 21 among fetuses aborted spontaneously being much higher.2,3In view of the absence
Cooley WC. Birth Incidence of Down Syndrome. Arch Ophthalmol. 1992;110(3):321. doi:10.1001/archopht.1992.01080150019010