Interpersonal Influences on Female Reproductive Endocrinology

Copyright ©1987 Clinical Practices in Sexuality, (3:8:24-28, 1987)

Winnifred B. Cutler, Ph.D.
Athena Institute for Women's Wellness

Onset of coital behavior, coital regularity and olfactory cues appear
to influence female fertility.

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Studies of animals and humans have created a body of evidence suggesting a role for pheromones in human sexuality.

The earlier studies of pheromones in lower mammals coupled to the more recent demonstrations of relationships between heterosexual behavior and reproductive endocrine response in humans combine to form the basis for subsequent research showing human pheromonal effects.

Heterosexual coital frequency and olfactory cues from men and other women appear to affect menstrual cycles and fertility status.

Menstrual Cycle Lengths Reflect Endocrine Milieu:

In 1971, Treloar and colleagues provided quantitative information on the menstrual cycle throughout life, based on 25,000 years of prospectively gathered data. There appear to be three distinct stages of menstrual cycling throughout the life of women: adolescent, reproductive viable, and premenopausal

Cycles of about 26-33 days are common during the reproductively viable years, although some women regularly have shorter and longer cycles. In contrast, the first seven (adolescent) and last seven (premenopausal) years are characterized by a very high incidence of long and short menstrual cycles, in addition to cycles of 26-33 days.

Subsequent studies by Vollman and others indicate that cycle lengths frequently reflect endocrine milieu and consequent fertility status. Cycles of about 29.5 +/- 3 days characterize a fertile, biophysical endocrine milieu while shorter or longer cycles have an increased incidence of infertile patterns.

Synchronized Reproductive Cycles:

McClintock (1971) found that female college students who live together for several months begin to cycle together. Subsequently, several investigators replicated that penomenon. ***

Sexual Behavior Affects Female Reproductive Endocrinology:

From 1979 through 1986 a series of studies were published which provided evidence for a role of heterosexual behavior in the development and maintenance of a fertile endocrine system in women.

One study investigated the first coital age of a private patient practice predominantly composed of women with infertility problems who had sought help at a specialty clinic at the University of Pennsylvnania. *** Women with increasingly greater degrees of infertility pathology showed increasingly later first coital ages. Women with primary infertility (with and without detectable pathology) had a mean age at first coitus that was 2.3 years older (20.6).

Moreover women who postponed their first coital experience more than seven years after the menarch (menses) were significantly more likely to be among the primary infertility group. This seven year "threshold" was particularly noteworthy in light of Treloar's demonstration of a seven year interval from menarch to the onset of regular fertile-type cycling. It was suggested that there might be a critical period for the onset of first coitus to optimize the likelihood of fertility.

In other studies, sexual behavior frequency was examined in five studies of women, in Philadelphia, PA and in Stanford, CA. All the studies showed a similar phenomenon.

When one separated the groups into women who engaged in weekly (never missing a nonmenstruating week of coitus) or less than weekly (either celibate or sporadic activity), those women who have regular weekly intercourse showed substantially higher incidences of fertile patterns of menstrual cyclicity

The fertility patterns were revealed in cycle length.

A menstrual cycle of less than 26 days was never observed among weekly active women while sexually less active women often showed short cycles. ** * Furthermore, women who had weekly intercourse had significantly higher levels of estrogen as well.

*** Further studies showed luteal phase lengths indicative of deficiencies...associated with sporadic sexual behavior, and particularly with infrequent or absent sexual activity in the luteal phase. Sporadic sexual behavior was further investigated in a sample of young college women who had prospectively recorded sexual behavior and cycle lengths. Women who where sporadically active...were more likely to show aberrant length menstrual cycles than those sporadically active women who showed lower amounts of coital exposure.

When sexual behavior was weekly or more, increased quantities did not alter the cycle length. When behavior was sporadic, increased quantities of behavior tended to disrupt the cycle.

In composite, the studies have shown that sex with men occurring in a consistent and regular pattern is associated with an increased incidence of fertile-type endocrine milieu.


Questions that emerge from these tentative conclusions are: What constitutes adequate sexual behavior? Is masturbation sufficient? Is intercourse necessary? What about homosexual behavior?

Tentative answers can be inferred from the data. Masturbation was shown in two separate studies not to be an adequate associate of the above-described fertile patterns of cycling; however, the presence of a man, either during noncoital genital stimulation or as a participant in sexual intercourse, was associated with the above-describe fertile endocrine patterns.

Until 1987, there were no data about the possible role of homosexual behavior on these phenomena, but the Kinsey Institute Group recently reported that lesbian sexual activity which occurs at least 3 times per week is also associated with cycle lengths of 29.5 days (Society for Menstrual Cycle Research 1987)

Because it was found that regular weekly patterns of heterosexual activity might influence menstrual cycle length, that women who lived together tended to cycle together, and because nonhuman studies suggested that chemical signals form other animals of the same species might be involved, an investigation was undertaken to evaluate whether an extract from the axillary region of men and women could offer a sufficient stimulus to induce changes in the menstrual cycle pattern of recipient women. The preliminary studies provided evidence indicating that axillary extracts from both sexes are effective.



To determine if olfactory cues are responsible for the influence of other people on womens' menstrual cycles and fertility status, studies were designed to determine if male essence makes aberrant length menstrual cycles less so and if female essence stimulates synchronization of normal cycles. ***

Twenty-nine women, 19-30 years of age, were enrolled in this study. All met the following criteria,: "gynecological maturity" (menstruating for at least 7 years) nulliparous, unmarried, not currently (nor within the last 3 months) using oral contraceptives or an IUD., and a willingness to make a daily entry of basal body temperature (BBT) and sexual behavior. ***

Among the group of women who began the experiment with aberrant length menstrual cycles, within the 14 weeks of the experiment male essence was effective in reducing the incidence of aberrant menstrual cycles. Both short and long cycles tended to become more normal in length.

Four of the women receiving placebo had cycles more aberrant than any of the woman receiving male extract, and all of the women receiving male extract appeared to be more bound in towards the fertile length cycle band. ***

Female essence was found to bring recipients' cycles into synchrony with the donors while placebo did influence the cycles of recipients.


Exogeneous influences on the fertility of women have now been demonstrated in a variety of ways. It appears that regular, stable patterns of sexual behavior are conducive to optimal fertility. The timing of sexual behavior, both via an adequately early onset and an ongoing regular pattern, appear to enhance and promote the fertile endocrine milieu of women. Likewise, regular sexual behavior also reduces perimenopausal symptomatology. In addition,olfactory cues appear to influence female reproductive endocrinology.

Acknowledgements and References available in full reprint/hard copy