To the Editor: In their Commentary on maternal age-based prenatal genetic counseling, Dr Berkowitz and colleagues1 state that “the majority of children with Down syndrome are born to younger mothers . . . ” This statement is incorrect. The percentage of pregnancies in women aged 35 years or older has tripled since 1975 and currently about 14% of births in the United States are to women aged 35 and older.2 The net result is that since about the year 2000, women aged 35 and older have accounted for slightly more than 50% of pregnancies with Down syndrome. This has significant implications for public health as well as the selection and evaluation of Down syndrome screening strategies based on maternal age, ultrasound, and serum analytes. Of further note, the current percentage of pregnancies to women aged 35 and older is virtually identical to the percentage of such pregnancies in 1933.2
Resta R. Maternal Age–Based Prenatal Genetic Testing. JAMA. 2006;296(8):930. doi:10.1001/jama.296.8.930-a
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