Immunocontraception outcome has focused on human chorionic gonadotropin (hCG). hCG is not necessary for fertilization, but is secreted by embryos shortly thereafter. Therefore, immunity against hCG does not prevent fertilization. However, it was found that anti-hCG antibodies prevent marmoset embryos from implanting in the endometrium of their mother's uterus. The main function of hCG is to sustain the ovarian corpus luteum during pregnancy past the time it would normally decay as part of the regular menstrual cycle. For the first 7–9 weeks in humans, the corpus luteum secretes the progesterone necessary to maintain the viability of the endometrium for pregnancy. Therefore,
Menstrual cycle by women during the peak of their fertility in the menstrual cycle. Moreover, women may demonstrate preference for men with a scent that indicates developmental stability. With regard to women's smell across the cycle, some evidence indicates that men use olfactory cues in order to know if a woman is ovulating. Using a rating of women's odors, women who are ovulating have been rated as more attractive by men. Men demonstrate preferences for the scent of fertile women. Preferences for facial features in mates can also change across the cycle. There has been no difference found in preference for long-term