Earlymenarche, late menopause, or late 1st pregnancy increases risk. Women who have a 1st pregnancy after age 30 are at higher risk than those who are nulliparous.
初潮早,停经晚,或首次妊娠晚,均可增加癌症危险。30岁后怀第一胎的妇女,其危险性要高于未产妇。
2
From the above statistics to see that the urban girls as early as the age of menarche in rural girls.