ReviewA meta-analysis provides evidence that prenatal smoking exposure decreases age at menarche

- A meta-analysis was used to examine association between an exposure to tobacco smoking in utero and age at menarche.
- Prenatal exposure to maternal smoking may decrease menarche onset by one month on average.
- Maternal smoking during pregnancy increases a risk of a daughter to have menarche before age of 11 by 15%.
- Caucasians and those who were born after 1965 have a higher risk of early age at menarche after prenatal exposure to maternal smoking.

Since studies of association between prenatal tobacco exposure and age at menarche have reported inconsistent results so far, we conducted a meta-analysis to examine this association. In total 36 relevant articles (1995-2014) were identified, 17 of which satisfied the inclusion criteria and were used in the analysis. Nearly one month decrease (−0.092 [95% CI:−0.160, −0.024] year) in age at menarche was found in women who were exposed to tobacco in utero. The meta-regression analysis showed that average year of birth in the cohorts might significantly influence association between maternal smoking and daughter's age at menarche. Based on results obtained from 5 studies where age at menarche was treated as a categorical variable, maternal smoking status during pregnancy increased a risk for daughters to have menarche earlier than at 11 years old by 15%.