Maternal passive smoking during pregnancy and age of menarche in daughters: a study of elementary and middle school students in Shanghai.

The objective of this study was to estimate the prevalence and determinants of passive smoking in pregnancy and to examine its association with an earlier age of menarche in offspring. This retrospective study enrolled 751 students 8 to 20 years old in Shanghai selected by stratified cluster sampling. Data were obtained through structured self-administered questionnaires and physical examinations. It was found that daughters with maternal tobacco exposure experienced relatively earlier menarche and had shorter cycle lengths, although both findings were not statistically significant. The unadjusted odds ratio for prenatal tobacco smoke exposure on the relatively earlier onset of menarche was 1.84 (95% confidence interval = 1.05-3.22) compared with no exposure, and the associations remained statistically significant after adjusting for birth weight, birth length, maternal age of menarche, and present height and weight. In conclusion, our study provides limited evidence supporting the hypothesis that maternal passive smoking during pregnancy leads to an earlier age of menarche of daughters.