Women's genital sexual arousal to oral versus penetrative heterosexual sex varies with menstrual cycle phase at first exposure

Reproductive-aged women show increased interest in sexual activity during the fertile phase of the menstrual cycle that can motivate sexual behavior and thereby increase the likelihood of conception. We examined whether women demonstrated greater sexual responses (subjective and genital sexual arousal) to penetrative versus oral sexual activities during the fertile versus non-fertile phases of their cycles, and whether women's arousal responses were influenced by the phase during which they were first exposed to these sexual stimuli (e.g., Slob et al., 1991; Wallen and Rupp, 2010). Twenty-two androphilic women completed two identical sexual arousal assessments in which genital responses were measured with a vaginal photoplethysmograph and their feelings of sexual arousal were recorded. Women viewed an array of 90 s films varying by couple type (female–female, male–male, female–male) and sexual activity type (oral or penetrative), during the fertile (follicular) and non-fertile (luteal) phases of their menstrual cycle, with the order of cycle phase at the first testing session counter-balanced. Women tested first in the fertile phase showed significantly greater genital arousal to female–male penetrative versus oral sex in both testing sessions, whereas self-reports of sexual arousal were not affected by cycle phase or testing order. These results contribute to a growing body of research suggesting that fertility status at first exposure to sexual stimuli has a significant effect on subsequent sexual responses to sexual stimuli, and that this effect may differ for subjective versus genital sexual arousal.     

Women's interest in visual sexual stimuli varies with menstrual cycle phase at first exposure and predicts later interest

This study investigated whether women's interest in visual sexual stimuli varied with their hormonal state. Viewing times of 30 women, 15 normal cycling (NC) and 15 oral contracepting (OC), to sexually explicit photos were measured at three different times. NC women were tested during their menstrual, periovulatory, and luteal phases, and OC women were tested at equivalent temporal intervals. Subjects viewed stimuli as long as desired, thus viewing time measured subject interest. Subjective ratings of stimulus sexual attractiveness were obtained on each test. There was no overall relationship between menstrual cycle phase and viewing time. However the participant's menstrual cycle phase during first exposure to sexual stimuli predicted subsequent interest in sexual stimuli during the next two tests. NC women who first viewed stimuli during their periovulatory phase looked longer at the sexual stimuli across all sessions than did women first tested in their luteal phase. OC women first exposed to the sexual stimuli during menstruation looked longer at the stimuli across all sessions than did OC women first exposed at other test phases. Neither current test phase nor initial cycle phase influenced subjective ratings. Women had increased interest in sexual stimuli across all sessions if first exposed to sexual stimuli when endogenous estrogens were most likely highest. These data suggest that women's interest in visual sexual stimuli is modulated by hormones such that the hormonal condition at first exposure possibly determines the stimuli's emotional valence, markedly affecting subsequent interest in sexual stimuli.     

Menstrual cycle-related changes in plasma oxytocin are relevant to normal sexual function in healthy women

Circulating levels of the neuro-hypophysial nonapeptide oxytocin increase during sexual arousal and orgasm in both men and women. A few studies have evaluated the effect of the menstrual cycle on plasma oxytocin in normally cycling, sexually active, healthy fertile women using or not using contraceptive pills. In 20 ovulating women and 10 women taking an oral contraceptive (group 1 and group 2, respectively), sexual function, hormonal profile, and plasma oxytocin (OT) were evaluated throughout the menstrual cycle. In group 1, plasma OT was significantly lower during the luteal phase in comparison with both the follicular and ovulatory phases. Plasma oxytocin was significantly correlated with the lubrication domain of the Female Sexual Function Index (FSFI) during the luteal phase and showed a trend towards statistical significance during the follicular phase. In group 2, plasma OT did not show any significant fluctuation throughout the menstrual cycle, even though a significant correlation was evident with both the arousal and the lubrication domain of the FSFI during the assumption of the contraceptive pill. These findings suggest that plasma OT fluctuates throughout the menstrual cycle in normally cycling healthy fertile women with adequate sexual activity but not taking any oral contraceptive pill. Moreover, plasma OT levels significantly relates to the genital lubrication in both women taking and not taking oral contraceptive pill apparently confirming its role in peripheral activation of sexual function.     

Neural activation in the orbitofrontal cortex in response to male faces increases during the follicular phase

Women's sexual interest changes with hormonal fluctuations across the menstrual cycle. It is unclear how hormones modify women's sexual behavior and desire, but one possibility is that they alter women's positive appraisals of stimuli and thus their sexual interest. Using 3 T fMRI, we measured neural activation in women at two time points in their menstrual cycle (late follicular, luteal) while they evaluated photos of men presented as potential sexual partners. Participants were ten heterosexual women aged 23-28 none of who was using hormonal contraceptives or in a committed relationship. In an event-related design, the women were presented with as series of photos of male faces and asked questions to assess their degree of sexual interest in the men depicted. Results demonstrate an overall effect of menstrual cycle phase on neural activation. During their follicular versus luteal phase, women demonstrated increased activation in the right medial orbitofrontal cortex (OFC), suggesting increased positive appraisal. Activation in the OFC was positively correlated with women's estradiol to progesterone ratios. There were no areas that demonstrated increased activation during the luteal versus follicular phase. The observed increase in activation in the OFC during the follicular phase may reflect a hormonally mediated increase in appetitive motivation and may prime women towards increased sexual interest and behavior around ovulation.     

Menstrual cycle phases and female receptivity to a courtship solicitation: an evaluation in a nightclub

Previous research has demonstrated that female behaviors toward men or sexual interest are different across the menstrual cycle. However, women's receptivity to an explicit courtship solicitation still remained in question. In a field experiment, 20-year-old women were approached by 20-year-old male confederates in nightclubs and solicited to dance during the period when slow songs were played. A survey was administered to the women in order to obtain information about the number of days since the onset of previous menses. It was found that women in their fertile phase agreed more favorably to the dance request than women in their luteal phase or in their menstrual phase.     

Sex differences in viewing sexual stimuli: an eye-tracking study in men and women

Men and women exhibit different neural, genital, and subjective arousal responses to visual sexual stimuli. The source of these sex differences is unknown. We hypothesized that men and women look differently at sexual stimuli, resulting in different responses. We used eye tracking to measure looking by 15 male and 30 female (15 normal cycling (NC) and 15 oral contracepting (OC)) heterosexual adults viewing sexually explicit photos. NC Women were tested during their menstrual, periovulatory, and luteal phases while Men and OC Women were tested at equivalent intervals, producing three test sessions per individual. Men, NC, and OC Women differed in the relative amounts of first looks towards, percent time looking at, and probability of looking at, defined regions of the pictures. Men spent more time, and had a higher probability of, looking at female faces. NC Women had more first looks towards, spent more time, and had a higher probability of, looking at genitals. OC Women spent more time, and had a higher probability of, looking at contextual regions of pictures, those featuring clothing or background. Groups did not differ in looking at the female body. Menstrual cycle phase did not affect women's looking patterns. However, differences between OC and NC groups suggest hormonal influences on attention to sexual stimuli that were unexplained by subject characteristic differences. Our finding that men and women attend to different aspects of the same visual sexual stimuli could reflect pre-existing cognitive biases that possibly contribute to sex differences in neural, subjective, and physiological arousal.     

Menstrual cycle shifts in attentional bias for courtship language

The current study investigated whether women show an attentional bias toward courtship language during the fertile phase of their menstrual cycle. Thirty heterosexual women (17 naturally cycling, 13 using hormonal contraceptives) completed a dichotic listening task on both a high and low fertility day of their menstrual cycle. Participants were asked to verbally repeat (shadow) an emotionally neutral target passage played in one ear while either a neutral or courtship distracter was played in the other ear. Courtship distracters were flirtatious in content but not overtly sexual. Shadowing errors were coded as a measure of attentional bias toward the distracter. Saliva samples were taken to determine whether levels of estradiol, progesterone and/or testosterone correlated with task performance. As predicted, naturally cycling women made more shadowing errors when listening to a courtship distracter during the fertile phase of their cycle than during the nonfertile phase. This effect was moderated by relationship status, such that fertile, mated women showed an attentional bias for courtship language but fertile single women did not. However, because of small sample sizes in the analysis, this relationship should be viewed as preliminary. Hormonal analysis revealed that higher levels of salivary estradiol predicted greater attentional bias toward courtship language in naturally cycling women. These results suggest that women's attention is drawn to verbal courtship signals when they are fertile, and that this shift is linked to increased estradiol release during the periovulatory phase.     

Why we haven't died out yet: changes in women's mimic reactions to visual erotic stimuli during their menstrual cycles

From an evolutionary point of view, female sexual desire contributes greatly to the success of reproduction by coordinating sexual behavior. It is known that female sexual desire fluctuates with the menstrual cycle. However, little is known about the role of basic emotions during menstrual cycle.We designed a facial EMG study to investigate facial expressions of joy during the menstrual cycle. 35 healthy women underwent 2 EMG sessions (T1 and T2). T1 took place in the follicular phase, T2 in the luteal phase. IAPS pictures of nude men (erotic stimuli) or of animals (control stimuli) were presented at both sessions. The activity of musculus zygomaticus major (responsible for expressing joy) was measured. We tested the hypothesis that zygomaticus activity is more pronounced in the follicular phase than in the luteal phase.The main result was that during the follicular phase, significantly more zygomaticus reactions were observed than during the luteal phase. This effect was restricted only to erotic stimuli. We concluded that an increased positive emotional responsiveness to erotic stimuli during the follicular phase is an important precondition for the probability of sexual activity during the conceptive days and thus for the success of reproduction.     

Fertility in the cycle predicts women's interest in sexual opportunism

Research over the past decade has documented clear, robust changes in women's sexual preferences and interests across the ovarian cycle. When fertile, women are particularly attracted to a number of masculine male features (e.g., masculine faces, voices, scents and bodies) and other traits, and especially when they evaluate men's “sexiness” rather than their attractiveness as long-term partners. The current research extended this line of research by examining changes in women's self-reported sexual interests across the cycle. We asked 68 normally ovulating women in committed romantic relationships to fill out questionnaires about their sexual preferences and interests (at that time, not in general) twice across their cycles: once when fertile and once during the luteal phase. Relative to during the luteal phase, fertile women expressed (a) greater emphasis on the physical attractiveness of a partner; (b) greater arousal at the sight or thought of attractive male bodily features; (c) greater willingness to engage in and interest in sex with attractive men, even ones who they do not know well (interest in sexual opportunism). These findings importantly extend our understanding of women's fertile-phase sexuality.     

Non-Advertized does not Mean Concealed: Body Odour Changes across the Human Menstrual Cycle

Females of a number of primate species display their fertile period by behavioural and/or morphological changes. Traditionally, the fertile period in human females has been considered to be concealed. However, this presumption has rarely been tested. One of the possible mechanisms for assessing menstrual cycle phase is through the sense of smell. In this study possible changes in odour across the menstrual cycle were investigated. Samples of body odour were acquired from 12 women (aged 19–27 yr), none of whom were using hormonal contraceptives. Samples were collected using cotton pads worn in the armpit for 24 h, from the menstrual, follicular and luteal cycle phases. Our experimental sample of 42 males (age 19–34 yr) repeatedly rated these odour samples for their intensity, pleasantness, attractiveness and femininity. Raw subjective smell ratings from each man were transformed to z‐scores. Subsequently, these z‐scores were tested by the general linear mixed‐model analysis (PROC MIXED, SAS) with the female's ID nested within the subject's ID as a random factor to account for the repeated measures of the subjects. Significant changes across the cycle were found for ratings of pleasantness [F_(2,689) = 702; p = 0.001], attractiveness [F(2,546) = 6.35; p = 0.002] and intensity [F(2,530) = 3.57; p = 0.028]. Odour from women in the follicular (i.e. fertile) phase was rated as the least intense and the most attractive. Subsequent post hoc analysis revealed significant differences in intensity, pleasantness and attractiveness between the menstrual phase and the follicular phase, and in pleasantness and attractiveness between the menstrual and luteal phases. Significant difference between the follicular and the luteal phase was found only for attractiveness. Our results suggest that men can potentially use smell as a mechanism for monitoring menstrual cycle phase in current or prospective sexual partners. Therefore, the fertile period in humans should be considered non‐advertized, rather than concealed.     

Localisation of the Notch family in the human endometrium of fertile and infertile women

To investigate the spatial and temporal immunolocalisation and staining intensity of the Notch signalling family in endometrium of fertile and infertile women, endometrial biopsies were collected by curettage from 25 fertile women across the menstrual cycle and 10 infertile women in the mid secretory phase of menstrual cycle. Immunohisotchemistry was completed for NOTCH1, -2, -3, -4, cleaved Notch, DLL1, -3, -4, JAGGED1, -2, HES and NUMB and immunostaining intensity measured in both the endometrial glandular and luminal epithelium. NOTCH1 and the ligands DLL1 and JAGGED1 were key proteins displaying increased staining intensity during the receptive phase of the menstrual cycle and dysregulated in infertile endometrium. Conversely, NUMB a negative regulator of Notch signalling was decreased in the mid secretory phase of the menstrual cycle in fertile women and increased with infertility.     

Menstrual cycle, pregnancy and oral contraceptive use alter attraction to apparent health in faces

Previous studies demonstrating changes in women's face preferences have emphasized increased attraction to cues to possible indirect benefits (e.g. heritable immunity to infection) that coincides with periods of high fertility (e.g. the late follicular phase of the menstrual cycle). By contrast, here we show that when choosing between composite faces with raised or lowered apparent health, women's preferences for faces that are perceived as healthy are (i) stronger during the luteal phase of the menstrual cycle than during the late follicular, fertile phase, (ii) stronger in pregnant women than in non-pregnant women and (iii) stronger in women using oral contraceptives than in women with natural menstrual cycles. Change in preference for male faces was greater for short- than long-term relationships. These findings indicate raised progesterone level is associated with increased attraction to facial cues associated with possible direct benefits (e.g. low risk of infection) and suggest that women's face preferences are influenced by adaptations that compensate for weakened immune system responses during pregnancy and reduce the risk of infection disrupting foetal development.     

Menstrual cycle, trait estrogen level, and masculinity preferences in the human voice

Men with low testosterone (feminine men) invest in relationships and offspring more than men with high testosterone (masculine men). Women's attraction to testosterone dependent traits (e.g. masculine face shape) is enhanced during the late-follicular, fertile phase of the menstrual cycle. Attractive, feminine women have stronger preferences for masculine men as possible long-term partners than less attractive, masculine women. We manipulated 2 testosterone related vocal traits (voice pitch and apparent vocal-tract length) in voices to test if women prefer masculinized men's voices to feminized men's voices; masculinity preferences are enhanced at the fertile (late-follicular) menstrual cycle phase; the amount that masculinity preferences shift cyclically relates to average estrone-3-glucuronide concentration (the primary urinary metabolite of estrone, E3G). We found women displayed general masculinity preferences for men's voices; masculinity preferences were greater in the fertile (late-follicular) phase of the cycle than the non-fertile (early-follicular and luteal) phase; and this effect was most pronounced for women with low average E3G concentration. As feminine women (i.e. those with high average E3G levels) are most able to obtain investment even from masculine men, these women may not need to change their mating preference or strategy during the menstrual cycle as much as masculine women.     

Expansion of CD4+CD25+and FOXP3+ regulatory T cells during the follicular phase of the menstrual cycle: implications for human reproduction

Regulatory T cells (Tregs) are thought to affect the severity of various infectious and autoimmune diseases. The incidence of autoimmune disease is higher in fertile women than in men. Thus, we investigated whether Treg numbers were modulated during the menstrual cycle by sex hormones. In fertile nonpregnant women, we detected an expansion of CD4(+)CD25(+)FOXP3(+) Tregs in the late follicular phase of the menstrual cycle. This increase was tightly correlated with serum levels of estradiol and was followed by a dramatic decrease in Treg numbers at the luteal phase. Women who have had recurrent spontaneous abortions (RSA) showed similarly low numbers of Tregs at both the follicular and luteal phases, comparable to numbers we observed in postmenopausal women. In addition to decreased numbers, Tregs from women with RSA were also functionally deficient, as higher numbers were required to exert a similar magnitude of suppression to CD4(+)CD25(+)FOXP3(+) cells from fertile women. Consequently, reproductive failure might result from the inability of Tregs in women with RSA to expand during the preimplantatory phase combined with their lower functional capacity. Additionally, the modulation of Treg numbers we observed in fertile women suggests that the stage of the menstrual cycle should be taken into account when Treg numbers are investigated clinically.     

Effects of Sexual Selection Upon Sperm Morphology and Sexual Skin Morphology in Primates

We review possible effects of sexual selection upon sperm morphology, and sexual skin morphology, in primates. Comparative morphometric studies, involving 31 species representing 21 primate genera, revealed a positive relationship between volume of the sperm midpiece, occurrences of multiple partner matings by females, and large relative testes sizes, which indicate sperm competition. The midpiece houses the mitochondria required to power sperm motility. Hence, sperm competition may have influenced the evolution of increased mitochondrial loading in species where females mate with multiple partners during the fertile period. Females of some Old World monkey species and female chimpanzees exhibit large estrogen-dependent sexual skin swellings during the follicular phase of the menstrual cycle. Studies of mandrills support the conclusion that swellings act primarily as sexually attractive, graded signals and that swelling size may indicate current reproductive quality. Measurements of the genitalia in chimpanzees indicate a secondary function for female swellings. The swelling increases the operating depth of the female's vagina by 50% during the fertile phase of her cycle. Males have evolved long, filiform penes capable of placing sperm close to the os cervix during competitive multipartner matings. This may exemplify how morphologic specializations in females can influence the coevolution of advantageous genitalic specializations in males: the phenomenon that Eberhard (1985) dubbed cryptic female choice.     

Head Tilt and Fertility Contribute to Different Aspects of Female Facial Attractiveness

Subjective attractiveness ratings of facial portraits of women taken at the fertile phase of the menstrual cycle are higher than those of portraits of the same women taken during non‐fertile periods. As female faces tilted downward are rated as more attractive and female courtship behaviours change across the menstrual cycle, we investigated whether systematic downward tilt of women's faces during the fertile phase might be responsible for increased attractiveness ratings. In the original study (Proc. R. Soc. Lond. B, 271, 2004, S272), the fertile‐phase portrait of each woman was deemed more attractive in 56–62% of cases. When the portraits were reclassified by head pitch, the more downward‐tilted portrait was preferred in 64–73% of cases. The fertile‐phase portrait was no more likely to be the downward‐tilted one, however, suggesting that effects of fertility on attractiveness are not simply due to changes in head position. We also had these portraits rated (N = 130) for physical attractiveness and behavioural allure. Fertile‐phase portraits were rated as more physically attractive than non‐fertile portraits, while more downward‐tilted portraits were rated as more behaviourally alluring than less downward‐tilted ones. These data not only confirm reported effects of head tilt and fertility on perceived female attractiveness, but also suggest that these factors influence different components of the attractiveness percept.     

The laws of Taharat HaMishpacha: potential effects on fertility

The laws of Taharat HaMishpacha (Family purity), which regulate coital activity among Orthodox Jews according to menstrual cycle phase in a population that generally does not use contraception, have potentially important effects on fertility. Analysis of these effects based on menstrual cycle and ovulatory phase lengths for women in the childbearing years shows that the majority of cycles are potentially exposed to coital activity during a fertile period and the increased likelihood of coitus following abstinence has a potentially fertility-enhancing effects. Since most Orthodox Jewish women complete the period of tumah (ritual impurity) and attend the mikveh (a ritual water immersion which marks the end of the cycle) on or before day 14 of the postmenstrual phase, only 22% of cycles are potential sources of diminished fertility as a result of restricted coitus. Any delay in the resumption of sexual relations would result in reduced fecundability for a much larger proportion of cycles. For example, if sexual relations are not resumed until day 15, the proportion of cycles wherein coitus is restricted to the postovulatory phase increases from a maximum of 30% to 41%. Observance of the laws do not greatly diminish the overall fertility of the population assuming that 1) the majority of tumah intervals do not extend beyond 14 days, and 2) coital activity is resumed immediately following return from mikveh. For the individual woman with a predominance of short cycles, delays in conception are probable.     

Decrease in sexual initiative and responsiveness in female rhesus macaques (Macaca mulatta) during pregnancy

Although the sexual behavior of female rhesus macaques (Macaca mulatta) has been reported to decrease during pregnancy, systematic studies have been largely confined to reports of male behavior. Therefore, we designed a study to examine changes in female sexual behavior during pregnancy. Six cycling multiparous female rhesus macaques were paired during the periovulatory period of the menstrual cycle and during the first and second halves of pregnancy with six sexually experienced males of the same species. Each female was paired with the same male in all tests. The means of the behavioral measures scored on days 11–13 of the menstrual cycle, 35–56 of pregnancy, and 147–168 of pregnancy were compared. Females showed a significant decrease in the present contact ratio and the rate of threat-aways during pregnancy. Males showed lower rates of threatening-away, contacting, mounting, intromitting, and ejaculating when females were pregnant. The extent to which the decrease in male sexual behavior can be accounted for by an increase in female rejection is uncertain, but it is probably as significant as any loss of attractiveness that might accompany pregnancy.     

Ovulatory shifts in human female ornamentation: near ovulation, women dress to impress

Humans differ from many other primates in the apparent absence of obvious advertisements of fertility within the ovulatory cycle. However, recent studies demonstrate increases in women's sexual motivation near ovulation, raising the question of whether human ovulation could be marked by observable changes in overt behavior. Using a sample of 30 partnered women photographed at high and low fertility cycle phases, we show that readily-observable behaviors - self-grooming and ornamentation through attractive choice of dress - increase during the fertile phase of the ovulatory cycle. At above-chance levels, 42 judges selected photographs of women in their fertile (59.5%) rather than luteal phase (40.5%) as "trying to look more attractive." Moreover, the closer women were to ovulation when photographed in the fertile window, the more frequently their fertile photograph was chosen. Although an emerging literature indicates a variety of changes in women across the cycle, the ornamentation effect is striking in both its magnitude and its status as an overt behavioral difference that can be easily observed by others. It may help explain the previously documented finding that men's mate retention efforts increase as their partners approach ovulation.     

Reproductive cycles of the talapoin monkey (Miopithecus talapoin).

Reproductive cycles of female talapoins living in caged breeding groups were followed over 7 years, using visible changes of the perineum. Changes in the perineum during the extended adolescence of this species are described. There was a clearly defined breeding season, although its onset was not so abrupt as in the wild. During the summer months females show very small perineal swellings or none at all. Even during the breeding season all stages of the follicular phase of cycles are highly variable. Completed menstrual cycles are relatively rare since talapoins are highly fertile; they may be somewhat shorter than fertile cycles. Cyclical activity is modifiable by social stimuli, and it is suggested that differences in synchrony of breeding between wild and captive populations might be due both to indequate climate cues and to a lower level of social stimulation in captivity. The concept of the menstrual cycle had limited value in predicting reproductive activity in this highly fertile seasonal breeder.