What is known about this phenomenon from studies in monkeys and women?
A number of studies in monkeys indicate that the vaginal epithelium of animals undergoes changes in thickness during various phases of the menstrual cycle. It is thickest prior to ovulation and thins out prior to menses. In animals treated with progesterone and synthetic progestins, thinning of the epithelium has been reported. A similar effect is noted in women, however. the situation is more complex. In women, menstrual cycle changes in the vaginal epithelium have been observed and are similar to what has been reported in monkeys. During pregnancy, thinning of the vaginal epithelium has been observed after the first trimester. Thinning is also observed during lactation. While vaginal thinning in this animal study was associated with increased infection rates of SIV, it may not be the only mechanism or even the most critical mechanism for infection. Other possible co-factors are changes in the immune system or changes in cervical mucus. Q: What kind of research is planned to determine
