英國癌症研究網這樣說

Breastfeeding lowers the risk of developing breast cancer, particularly if you have your children when you are younger. The longer you breastfeed the more the risk is reduced.

顯然，工作壓力大的年輕女性常常會晚婚晚育，有了孩子常常無法母乳喂養，所以乳腺癌風險就高。