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

The ovulatory phase is the day of the LH surge onset and the two subsequent days (LH day 0 to 2). The length of this phase is fixed at 3 days because it is well established in the literature that ovulation occurs 30 2 hours after the onset of the LH surge in a urine sample (Baviera et al., 1988; Stern & McClintock, 1995). The LH surge and subsequent ovulation mark the anatomical and hormonal transition from predominance of estrogen produced by the developing follicle to the predominance of progesterone produced by the corpus luteum. During this phase, vaginal secretions are more profuse and are typically thin, watery, and clear. The specific type of stretchable, thread-like mucus, spinnbarkheit, occurs at this time. Basal body temperature rises at this end of this phase. FSH, as well as LH, peaks at this time. Circulating levels of testosterone are often greatest during this phase as well.

The early luteal phase includes LH day 3 through premenses day--4. Vaginal secretions may return to dry or thick at this time. Basal body temperature is typically from 0.3 to 1.0 degree higher relative to the follicular phase during this time. The early luteal phase is dominated by progesterone.

The late luteal phase consists of the 3 days before menses onset (premenses days--3 to--1). During this phase the corpus luteum is regressing, accompanied by falling levels of progesterone. Similar to the early luteal phase, vaginal secretions may be dry and thick and basal body temperature is relatively high, falling prior to menses onset.

EXPERIMENTAL PROTOCOL

We used the following protocol for both Study 1 and Study 2. Specific details unique to each study, such as sample size and additional measures, are presented in the study methods sections.

Participants

Participants in both studies were healthy women between the ages of 18 and 35 years who were currently having typical spontaneous menstrual cycles (24-34 days long). The women were recruited through posters and fliers on the campus of a major midwestern university, and through advertisements in community newspapers. They were blind to the purpose of this study (sexual motivation) since the advertisements stated that the study was about olfactory acuity and the menstrual cycle.

The women accepted into the study had a history of regular menstrual cycles, were not using birth control pills or an IUD, and had never been pregnant. In addition, they reported they were not taking prescription or nonprescription drugs on a regular basis and were not experiencing psychiatric disorders. Participants were measured and weighed to ensure that they were within 30% of normal height-to-weight ratio. We collected data regarding exercise types and duration on a daily basis. Participants also agreed to use only barrier contraception and were planning not to become pregnant during the study period. All participants participated on a voluntary basis and were paid a sum approved by the Institutional Review Board at The University of Chicago.