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 use of birth control pills should affect eating behaviour as they minimise or remove the fluctuations in hormone levels. The neurotransmitter serotonin is also thought to play a role in food intake. Serotonin is responsible for inhibiting eating and controlling meal size, among other things, and is modulated in part by ovarian hormones. A number of factors affect whether dieting will affect these menstrual processes: age, weight loss and the diet itself. First, younger women are likely to experience menstrual irregularities due to their diet. Second, menstrual abnormalities are more likely with more weight loss. For example, anovulatory cycles can