Menstrual cycle phase and sexual arousability in women

Sexual arousability of women has not been consistently found to vary significantly over phases of the menstrual cycle. We studied changes in the temperature of a labium minus and subjective sexual and genital arousal recorded on semantic scales while watching erotic video in 12 women with natural menstrual cycles and 12 women using low-dose estrogen oral contraceptive pills. Natural cycle phase was ascertained by blood progesterone. Subjects were tested twice, with an interval of about 2 weeks. Half of each group had their first test during their luteal phase, the others during their follicular phase. Women tested for the first time in their follicular phase were sexually more aroused than women tested for the first time during their luteal phase. This was true for both objective (i.e., a labium minus change in temperature) and subjective genital arousal. When these women were retested in their alternative phase of the menstrual cycle, those who were then follicular did not score higher than those who were then luteal. On the contrary, the latter group scored as high as when tested during their follicular phase. This phenomenon was observed both in women with and without oral contraception. The nature of the menstrual phase (i.e., natural or pill-induced) seems irrelevant in this respect. Sexual arousal achieved during the first session appeared to be correlated with an increase in desire for making love during the rest of the day and night. Only 1 of 12 women tested during their luteal phase indicated an increase in desire to make love, while 6 of 12 women tested during their follicular phase indicated an increase. Apparently the menstrual cycle phase during the first test determines the immediate response and indirectly affects the response during the second test approximately 10 days later. In a random block design the difference in sexual response between follicular and luteal phase of the menstrual cycle disappears.