Maternal use of oral contraceptives and Down syndrome.

The date of stopping oral contraceptives (OC) in relation to the last menstrual period was studied in 458 women with Down syndrome infants born in 1983-1986 and compared with the expected distribution estimated from the total population of births for these years, after stratification for year of birth, maternal age, and parity. No deviations were seen for the total group, for women less than 30 or 30+ years old, or for Down syndrome infants with known trisomy 21. This is the third study showing no effect and in contrast to the only study which indicates an association between OC use and the birth of an infant with Down syndrome.