The attitude of civilization is sterilization was also achieved through the sterilization of the female population. Bokanovsky's Process made it possible for the Brave New World to control the amount of fertile women in society. Even with the advancement of scientific technology human ovaries were still needed for the manufacturing of embryos. Fertile women were encouraged to undergo a hysterectomy. In return for selling their ovaries, women received six months pay. Around seventy percent of the women in Brave New World were infertile. These women were called freemartins. Freemartins were produced through injecting female embryos with a dose of a male sex-hormone.