I think she is refering to the fact that the fringes residents are forcibly rendered unable to reproduce prior to being exiled to the fringes. As (from what I remember of the book) surgery isn’t very advanced in their culture this probably leaves the males incapable of the act, so there isn’t the same risk of interference to the women.
(To clear a related plot point Sophie’s lover escaped to the fringes and wasn’t operated on.)