Women's sexual experience during the menstrual cycle: identification of the sexual phase by noninvasive measurement of luteinizing hormone

Journal of Sex Research, Feb, 2004 by Susan B. Bullivant, Sarah A. Sellergren, Kathleen Stern, Natasha A. Spencer, Suma Jacob, Julie A. Mennella, Martha K. McClintock

Here we present two studies designed to improve upon these methodological shortcomings and inconsistencies. The participants were fertile women who were not taking the birth control pill, but who were trying to avoid pregnancy and were using barrier contraception. Thus, reproductive hormones were not being artificially regulated and in addition, detection of a peak in sexual activity around ovulation would not be an artifact of a woman trying to conceive. Both studies used a novel, noninvasive method for pinpointing the timing of the preovulatory LH surge with high accuracy and thus demarcating the follicular, ovulatory, and luteal phases, in addition to menses. In Study 1, this method was used to assess the frequency of sexual activity across the cycle and to compare the patterns of female and male initiation. Study 2 assessed sexual activity as well and focused on the variation in subjective sexual experience throughout the menstrual cycle. It also quantified the effects of having a stable sexual partner and general feelings of loneliness. The two studies enabled robust conclusions because they reproduced the basic findings using complementary yet independent methods.

A NONINVASIVE METHOD FOR PRECISELY IDENTIFYING PHASES OF THE MENSTRUAL CYCLE

Multiple Indicators of Menstrual Cycle Phase

The menstrual cycle, or the interval between two consecutive menses, is the biologically coherent unit of analysis for the human ovarian cycle (Spencer, Jacob, & McClintock, 2003). It is comprised of recruitment, selection, and growth of ovarian follicles, ovulation, transformation of the ruptured follicular tissue into a functional corpus luteum, and finally the death of the corpus luteum and the subsequent menses. The midcycle surge of luteinizing hormone (LH) is tightly coupled to ovulation (preceding it in urine by 30 [ or -] 2 hours), and together they demarcate the transition from the estrogen-predominant follicular phase to the progesterone-dominant luteal phase. Ovulation and the associated dramatic change in hormonal profiles can be confirmed retrospectively by documenting high levels of progesterone produced by the functional corpus luteum.

This sequence of anatomical and hormonal events reliably changes the type of vaginal secretions and cervical mucus in all phases of the cycle and also increases basal body temperature (BBT) during the luteal phase. Although erroneously considered imprecise indicators of ovulation and menstrual cycles phase (reviewed by Stern & McClintock, 1998), changes in specific aspects of these characteristics are indeed correlated with LH surge onset when measured with our revised method described here. Thus, they can in fact be used as valid indicators of the LH surge onset, ovulation, and the associated cyclic changes in ovarian hormones, and they are particularly useful when hormonal data are unavailable or impractical to obtain.

Here we present a noninvasive method for precisely demarcating the hormonally distinct phases of the menstrual cycle. The precision of this method relies on revised methods for not only collecting urine, vaginal secretions, and temperature data, but also analyzing these samples and interpreting the results. Therefore, we asked participants to call the laboratory on the day they first experienced menstrual bleeding and again each day they had a positive LH urine test. They were then instructed on which days to collect three daily urine samples during the middle of their luteal phase. Throughout the entire menstrual cycle, they recorded daily the characteristics of their vaginal secretions and cervical mucus as well as their basal body temperature.