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The puberty lessons included information about personal care during menstruation .

青春期教育包括月经期间个人护理品的相关信息。

Period pain is caused by contractions in the womb during menstruation .

痛经是由月经期间女性的子宫收缩引起的。

If not , the egg and lining are shed during menstruation .

如果没有受精，卵和子宫自壁就会在月经期脱落。

Our findings also indicate a genetic basis for the associations between early menstruation and both height and bmi .

我们的发现也显示了月经提前与身高和身体重量指数关系的基因基础。

Talking about menstruation or wet dreams after they 've already started means you 're too late .

如果你的孩子已经来了月经或者出现了梦遗，你再跟他们谈就晚了。