[Oral contraceptive and trisomy 21. A retrospective study of 730 cases (author's transl)].

A retrospective study of 730 cases of trisomy 21 and of 1 035 cases of abnormal children without a detectable chromosomal aberration, allows the study of the frequency of use of oral contraceptives by their mothers. The statistical analysis shows no notable differences for mothers 30 years old and younger. Among the mothers 30 to 38 years old, there is an excess of pill-taking by mothers of trisomy 21 children. For this second category of mothers (30 to 38 years) this excess is significant (a) when the delay between the cessation of pill-taking and the conception of the child is six months or less ; (b) when the duration of pill-taking has been longer than one year ; and (c), when those two factors are present simultaneously. Moreover, the frequency of males is significantly reduced in trisomy 21 children when their mother have taken the pill. As a whole, for the subsample of mothers 30 and older, a correlation is observed between the three factors analysed, pill-taking, sex ratio, and trisomy 21. In view of the fact that decrease of the sex ratio and the increase of the frequency of trisomy 21 both are correlated with maternal aging in the general population, it seems remarkable that a correlation between these two variables and the use of oral contraceptives is observed only when the women had already passed the first half of their reproduction period.