An Objective Measure of Vaginal Lubrication in Women With and Without Sexual Arousal Concerns.

Changes in vaginal blood flow and lubrication are primary components of physiological sexual arousal in women. Despite the existence of well-established tools for measuring vaginal blood flow, there is not yet a consistently implemented measure of physiological lubrication. To address this methodological gap, researchers have begun examining the utility of litmus test strips, primarily in sexually healthy women. The present study builds on this work by examining the utility of an alternative tool, the Schirmer Tear Test strips, in women with (n = 32) and without (n = 32) sexual arousal concerns. Significant increases in physiological lubrication were found in response to a sexual film, and these changes were moderately correlated with self-reported genital arousal (r = .41) and lubrication (r = .30). No between-group differences in lubrication were observed. These results indicate the Schirmer Tear Test strips are sensitive enough to detect increases in lubrication and may be valuable in clinical and research assessments of female sexual arousal.

Post-copulatory genetic matchmaking: HLA-dependent effects of cervical mucus on human sperm function.

Several studies have demonstrated that women show pre-copulatory mating preferences for human leucocyte antigen (HLA)-dissimilar men. A fascinating, yet unexplored, possibility is that the ultimate mating bias towards HLA-dissimilar partners could occur after copulation, at the gamete level. Here, we explored this possibility by investigating whether the selection towards HLA-dissimilar partners occurs in the cervical mucus. After combining sperm and cervical mucus from multiple males and females (full factorial design), we found that sperm performance (swimming velocity, hyperactivation, and viability) was strongly influenced by the male-female combination. This indicates that sperm fertilization capability may be dependent on the compatibility between cervical mucus (female) and sperm (male). We also found that sperm viability was associated with partners' HLA dissimilarity, indicating that cervical mucus may selectively facilitate later gamete fusion between immunogenetically compatible partners. Together, these results provide novel insights into the female-mediated sperm selection (cryptic female choice) in humans and indicate that processes occurring after copulation may contribute to the mating bias towards HLA-dissimilar partners. Finally, by showing that sperm performance in cervical mucus is influenced by partners' genetic compatibility, the present findings may promote a deeper understanding of infertility.

Conditionally reprogrammed macaque endocervical cells retain steroid receptor expression and produce mucus.

Cervical mucus produced by the endocervix plays an essential role as a hormonally induced regulator of female fertility. Cervical mucus fluctuates in both physical characteristics and in sperm penetrability in response to estrogens and progestogens. However, the mechanisms by which steroid hormones change mucus remains poorly understood. Current in vitro models have limited capability to study these questions as primary endocervical cells possess limited expansion potential, and immortalized cells lose in vivo characteristics such as steroid sensitivity. Here we overcome these limitations by establishing an in vitro primary endocervical cell culture model using conditionally reprogrammed cells (CRCs). CRC culture utilizes a Rho-kinase inhibitor and a fibroblast feeder layer to expand proliferative potential of epithelial cell types that have normally short in vitro life spans. In our studies, we produce CRC cultures using primary endocervical cells from adult female rhesus macaques (Macaca mulatta). We demonstrate that primary endocervical cells from the nonhuman primate can be robustly expanded using a CRC method, while retaining steroid receptor expression. Moreover, when removed from CRC conditions and switched to differentiation conditions, these cells are able to differentiate and produce mucus including MUC5B, the most prevalent mucin of the endocervix. We conclude that this method provides a promising in vitro platform for conducting mechanistic studies of cervical mucus regulation as well as for screening new therapeutic targets for fertility regulation and diseases of the endocervix.

Comparison of woman-picked, expert-picked, and computer-picked Peak Day of cervical mucus with blinded urine luteinising hormone surge for concurrent identification of ovulation.

BACKGROUND: Previous research has demonstrated that women instructed in fertility awareness methods can identify the Peak Day of cervical mucus discharge for each menstrual cycle, and the Peak Day has high agreement with other indicators of the day of ovulation. However, previous studies enrolled experienced users of fertility awareness methods or were not fully blinded. OBJECTIVE: To assess the agreement between cervical mucus Peak Day identified by fertile women without prior experience on assessing cervical mucus discharge with the estimated day of ovulation (1 day after urine luteinising hormone surge). METHODS: This study is a secondary analysis of data from a randomised trial of the Creighton Model FertilityCareTM System (CrM), conducted 2003-2006, for women trying to conceive. Women who had no prior experience tracking cervical mucus recorded vulvar observations daily using a standardised assessment of mucus characteristics for up to seven menstrual cycles. Four approaches were used to identify the Peak Day. The referent day was defined as one day after the first identified day of luteinising hormone (LH) surge in the urine, assessed blindly. The percentage of agreement between the Peak Day and the referent day of ovulation was calculated. RESULTS: Fifty-seven women with 187 complete cycles were included. A Peak Day was identified in 117 (63%) cycles by women, 185 (99%) cycles by experts, and 187 (100%) by computer algorithm. The woman-picked Peak Day was the same as the referent day in 25% of 117 cycles, within ±1 day in 58% of cycles, ±2 days in 84%, ±3 days in 87%, and ±4 days in 92%. The ±1 day and ± 4 days' agreement was 50% and 90% for the expert-picked and 47% and 87% for the computer-picked Peak Day, respectively. CONCLUSIONS: Women's daily tracking of cervical mucus is a low-cost alternative for identifying the estimated day of ovulation.

NK cells not only in endometrium but also in ovulatory cervical mucus in patients with decreased fertility.

OBJECTIVE: An increased number of NK cells is associated with autoimmune disorder and is known to play a role in infertility. The aim of our research was to monitor the density of NK cells CD56+ and CD16+ in ovulatory cervical mucus (OCM) and in endometrium in infertile women as well as in connection with the actual status of antibodies against phospholipids, sperm and HHV-6 antibodies. TYPE OF STUDY: Original aticle. SETTING: Genetika - Plzeň. METHODS: Seventy-two randomly selected women aged 20-39 (mean age: 32.3) years old resulted in fifty-seven patients with repeated unexplained miscarriages, and fifteen fertile healthy women. The hormonal status was studied including ovulation, the humoral autoimmune responses to eight phospholipids, trombophilia, karyotyping, hysteroscopy, and endometrium immunohistology. Patients were without any clinical and laboratory symptoms of vaginitis at the time of OCM sampling and endometrium study. In one patient antiphospholipid syndrome was present, and in one woman diabetes mellitus was identified. Uterine NK cells CD56+ , CD16+ and NK cells in OCM were identified by immunocytochemistry, antiphospholipid antiboides by ELISA. We used indirect MAR-test for study of local spermagglutinating antibodies in OCM. Indirect immunofluorescent method was used for detection of serum and OCM IgM, IgG antibodies against HHV-6 levels at the time of ovulation. RESULTS: We found both high density of NK cells CD56+ and CD16+ in OCM and in endometrium in only two infertile women with repeated abortions. NK cells in OCM were missing in other samples of patients. The prevalence of high density of NK cells CD56+ in the endometrium was seen in twenty three (40%), NK cells CD16+ in eleven (19%), NK cells 56+ and NK cells 16+ together in eight (14%). Levels of serum and OCM IgG against HHV-6 in all examined patients were not elevated, no cervical sperm antibodies were found. CONCLUSION: We compared density of NK cells CD56+ and CD16+ in OCM and secretory endometrium in all infertile patients. Our results show that cell mucosal activity in the cervical area at the time of ovulation in two infertile patients was evident. We excluded the abnormal number of NK cells owing to local and general viral infection (HHV-6). But our question still remains - are cervical NK cells fixed or still migrating from endometrium into OCM? New research is planned.

Characterization of the cervical mucus plug in mares.

The cervical mucus plug (CMP) is believed to play an integral role in the maintenance of pregnancy in the mare, primarily by inhibiting microbial entry. Unfortunately, very little is known about its composition or origin. To determine the proteomic composition of the CMP, we collected CMPs from mares (n = 4) at 9 months of gestation, and proteins were subsequently analyzed by nano-LC-MS/MS. Results were searched against EquCab2.0, and proteomic pathways were predicted by Ingenuity Pathway Analysis. Histologic sections of the CMP were stained with H&E and PAS. To identify the origin of highly abundant proteins in the CMP, we performed qPCR on endometrial and cervical mucosal mRNA from mares in estrus, diestrus as well as mares at 4 and 10 m gestation on transcripts for lactotransferrin, uterine serpin 14, uteroglobin, uteroferrin, deleted in malignant brain tumors 1 and mucins 4, 5b and 6. Overall, we demonstrated that the CMP is composed of a complex milieu of proteins during late gestation, many of which play an important role in immune function. Proteins traditionally considered to be endometrial proteins were found to be produced by the cervical mucosa suggesting that the primary source of the CMP is the cervical mucosa itself. In summary, composition of the equine CMP is specifically regulated not only during pregnancy but also throughout the estrous cycle. The structural and compositional changes serve to provide both a structural barrier as well as a physiological barrier during pregnancy to prevent infection of the fetus and fetal membranes.

Assessment of vulvar discomfort with sexual activity among women in the United States.

BACKGROUND: Multidimensional self-report measures of sexual function for women do not include the assessment of vulvar discomfort, limiting our understanding of its prevalence. In an effort to improve the measurement of patient-reported health, the National Institutes of Health funded the creation of the Patient Reported Outcomes Measurement Information System (PROMIS). This included the development of the PROMIS Sexual Function and Satisfaction measure, and version 2.0 of the Sexual Function and Satisfaction measure included 2 scales to measure vulvar discomfort with sexual activity. OBJECTIVES: The objectives of the study were to describe the development of 2 self-reported measures of vulvar discomfort with sexual activity, describe the relationships between these scales and scales for lubrication and vaginal discomfort, and report the prevalence of vulvar discomfort with sexual activity in a large, nationally representative sample of US women. STUDY DESIGN: We followed PROMIS measure development standards, including qualitative development work with patients and clinicians and psychometric evaluation of candidate items based on item response theory, in a probability sample of 1686 English-speaking US adult women. We tested 16 candidate items on vulvar discomfort. We present descriptive statistics for these items, correlation coefficients among the vulvar and vaginal scales, and mean PROMIS scores with 95% confidence intervals separately by menopausal status for the 1046 women who reported sexual activity in the past 30 days. RESULTS: Based on the psychometric evaluation of the candidate items, we created 2 separate 4 item scales, one to measure labial discomfort and pain and one to measure clitoral discomfort and pain. Additional items not included in the scales assess pain quality, numbness, and bleeding. The correlations between the lubrication, vaginal discomfort, and the 2 vulvar discomfort measures ranged from 0.46 to 0.77, suggesting that these measures represent related yet distinct concepts. In our nationally representative sample, 1 in 5 US women endorsed some degree of vulvar discomfort with sexual activity in the past 30 days. Menopausal status was associated with lower lubrication and higher vaginal discomfort but not with vulvar discomfort. CONCLUSION: The PROMIS Vulvar Discomfort with Sexual Activity-Labial and Vulvar Discomfort with Sexual Activity-Clitoral scales are publicly available for use in research and clinical settings. There is limited overlap between vulvar discomfort and lubrication or vaginal discomfort. The importance of measuring vulvar discomfort as part of a comprehensive assessment of sexual function is underscored by its prevalence.

Identification of lactoferrin and glutamate receptor-interacting protein 1 in bovine cervical mucus: A putative marker for oestrous detection.

Accurate detection of oestrus is important for artificial insemination. The aim of this study was to identify oestrous-specific bovine cervical mucus proteins that could be used to determine the optimal time for artificial insemination. Non-oestrous and controlled internal drug release (CIDR)-induced oestrous-stage mucus proteins were purified and subjected to surface-enhanced laser desorption/ionization time-of-flight mass spectrometry, sodium dodecyl sulphate polyacrylamide gel electrophoresis and MALDI-TOF/TOF. Among differentially expressed proteins, lactoferrin (LF) and glutamate receptor-interacting protein 1 (GRIP1) showed a twofold increase during the CIDR-induced oestrous stage compared to the levels in non-oestrous stage in bovine cervical mucus. The RT-PCR, Western blotting and immunohistochemistry results showed that LF and GRIP1 expression was significantly increased during the oestrous stage in the uterus. This study demonstrated that bovine LF and GRIP1 exist during the oestrous stage, but not during the non-oestrous stage, suggesting that cervical mucus LF and GRIP1 are useful oestrous detection markers in cattle.

Assessment of the quality of cervical mucus among users of the levonorgestrel-releasing intrauterine system at different times of use.

BACKGROUND AND OBJECTIVES: The quality of cervical mucus (CM) among the levonorgestrel-releasing intrauterine system (LNG-IUS) users is controversial. The objectives were to assess CM compared to the levels of oestradiol (E2) and the frequency of cycles with luteal activity among users of the LNG-IUS. MATERIALS AND METHODS: In total, 224 LNG-IUS users for between two months and five years were recruited at a Brazilian family planning clinic. For the cross-sectional part of the study, we enrolled 175 LNG-IUS users at 2, 6 12, 24, 36, 48, and 60 months after insertion (25 women in each group), and we performed one evaluation. For the prospective part of the study, we enrolled 49 LNG-IUS users at the same lengths of use after insertion (7 women in each group), and we evaluated these women once a week for five consecutive weeks. . RESULTS: Mean (± SEM) CM scores of all evaluations among women with single and weekly evaluations were between 3.3 ± 0.9 and 8.5 ± 0.3, respectively independently of the length of use of the LNG-IUS. Mean E2 values ranged from 45.5 ± 6.8 to 472.5 ± 34.7 pg/ml and the maximum ovarian follicle diameter on the days of evaluation varied from 14.0 ± 1.3 to 31.2 ± 0.4 mm. CONCLUSIONS: The mean CM score of all evaluations, independent of the length of use of the LNG-IUS and normal levels of serum E2, was below 10 was according to the WHO is inadequate for sperm penetration.

The role of the cervix in fertility: is it time for a reappraisal?

Knowledge regarding the role of the cervix in fertility has expanded considerably over the past 20 years and in this article, we propose that it is now time for its function to be reappraised. First, we review the anatomy of the cervix and the vaginal ecosystem that it inhabits. Then, we examine the physiology and the role of the cervical mucus. The ongoing mystery of the exact mechanism of the sperm-cervical mucus interaction is reviewed and the key players that may unlock this mystery in the future are discussed. The soluble and cellular biomarkers of the lower female genital tract which are slowly being defined by contemporary research are reviewed. Attempts to standardize these markers, in this milieu, are hindered by the changes that may be attributed to endogenous or exogenous factors such as: age, hormonal changes during the menstrual cycle, ectropion, infection, smoking and exposure to semen during sexual intercourse. We review what is known about the immunology of the cervix. With the widespread use of large loop excision of the transformation zone (LLETZ) for treatment of cervical intraepithelial neoplasia, the anatomy of the cervix is changing for many women. While LLETZ surgery has had very positive effects in the fight against cervical cancer, we debate the impact it could have on a woman's fertility.

Seminal plasma aids the survival and cervical transit of epididymal ram spermatozoa.

Seminal plasma purportedly plays a critical role in reproduction, but epididymal spermatozoa are capable of fertilisation following deposition in the uterus, calling into question the biological requirement of this substance. Through a combination of direct observation of spermatozoa in utero using probe-based Confocal Laser Endomicroscopy, in vivo assessment of sperm fertility and in vitro analysis of various sperm functional parameters, this study investigated the role of seminal plasma in spermatozoa transit through the cervix of the ewe. Following deposition in the cervical os, epididymal spermatozoa previously exposed to seminal plasma displayed an enhanced ability to traverse the cervix as evidenced by both significantly higher pregnancy rates and numbers of spermatozoa observed at the utero-tubal junction when compared with epididymal spermatozoa not previously exposed to seminal plasma. The beneficial effect of seminal plasma on sperm transport was clearly localised to transit through the cervix as pregnancy rates of spermatozoa deposited directly into the uterus were unaffected by exposure to seminal plasma. This phenomenon was not explained by changes to sperm motion characteristics, as seminal plasma had no effect on the motility, kinematic parameters or mitochondrial membrane potential of spermatozoa. Rather, in vitro testing revealed that seminal plasma improved the ability of epididymal spermatozoa to penetrate cervical mucus recovered from ewes in oestrus. These results demonstrate that the survival and transport of ram spermatozoa through the cervix of the ewe is not linked to their motility or velocity but rather the presence of some cervical penetration trait conferred by exposure to seminal plasma.

The cervical mucus plug inhibits, but does not block, the passage of ascending bacteria from the vagina during pregnancy.

OBJECTIVE: To evaluate the microbial load and the inflammatory response in the distal and proximal parts of the cervical mucus plug. DESIGN: Experimental research. POPULATION: Twenty women with a normal, singleton pregnancy. SAMPLE: Vaginal swabs and specimens from the distal and proximal parts of the cervical mucus plug. METHODS: Immunohistochemistry, enzyme-linked immunosorbent assay, quantitative polymerase chain reaction and histology. RESULTS: The total bacterial load (16S rDNA) was significantly lower in the cervical mucus plug compared with the vagina (p = 0.001). Among women harboring Ureaplasma parvum, the median genome equivalents/g were 1574 (interquartile range 2526) in the proximal part, 657 (interquartile range 1620) in the distal part and 60,240 (interquartile range 96,386) in the vagina. Histological examinations and quantitative polymerase chain reaction revealed considerable amounts of lactobacilli and inflammatory cells in both parts of the cervical mucus plug. The matrix metalloproteinase-8 concentration was decreased in the proximal part of the plug compared with the distal part (p = 0.08). CONCLUSION: The cervical mucus plug inhibits, but does not block, the passage of Ureaplasma parvum during its ascending route from the vagina through the cervical canal.

Pilot test and validation of the peak day method of prospective determination of ovulation against a handheld urine hormone monitor.

BACKGROUND: Transient exposures may influence fertility and early embryonic development. To assess the time of conception in vivo and conduct concurrent biomonitoring, ovulation must be identified prospectively. We report on the development and validation of a simple, prospective method, the Peak Day method, to determine likely day of ovulation based upon daily observations of cervical fluid. METHODS: We recruited 98 women to learn the Peak Day method from a brochure, 26 of whom concurrently used the method with blinded daily urine hormone monitoring (estrone glucuronide and luteinizing hormone). All women were instructed to complete an exposure questionnaire immediately upon identifying ovulation. Briefly, the exposure questionnaire captured time-varying and transient exposures such as medication use, water consumption, and amount of sleep. We assessed timely completion of the exposure questionnaire, agreement of women's estimated day of ovulation (EDO) and the EDO by expert review, and agreement between the EDO by expert review and by blinded urine monitoring. RESULTS: Of 147 cycles evaluated, women selected an EDO in 130 (88%) and subsequently completed the periovulatory exposure questionnaire in 122 (94%) cycles. Of the 26 cycles evaluated with blinded hormonal monitoring, the Peak Day "best quality" algorithm, based upon cervical fluid, identified ovulation ± 3 days of the urine monitor in 24 cycles (92%). CONCLUSIONS: With simple written instructions, women can identify an estimated day of ovulation and perform periovulatory exposure assessment. The Peak Day method is highly cost-effective and could be applied by researchers to target periconceptional or very early developmental stage exposure assessment.

Nanoparticles reveal that human cervicovaginal mucus is riddled with pores larger than viruses.

The mechanisms by which mucus helps prevent viruses from infecting mucosal surfaces are not well understood. We engineered non-mucoadhesive nanoparticles of various sizes and used them as probes to determine the spacing between mucin fibers (pore sizes) in fresh undiluted human cervicovaginal mucus (CVM) obtained from volunteers with healthy vaginal microflora. We found that most pores in CVM have diameters significantly larger than human viruses (average pore size 340 +/- 70 nm; range approximately 50-1800 nm). This mesh structure is substantially more open than the 15-100-nm spacing expected assuming mucus consists primarily of a random array of individual mucin fibers. Addition of a nonionic detergent to CVM caused the average pore size to decrease to 130 +/- 50 nm. This suggests hydrophobic interactions between lipid-coated "naked" protein regions on mucins normally cause mucin fibers to self-condense and/or bundle with other fibers, creating mucin "cables" at least three times thicker than individual mucin fibers. Although the native mesh structure is not tight enough to trap most viruses, we found that herpes simplex virus (approximately 180 nm) was strongly trapped in CVM, moving at least 8,000-fold slower than non-mucoadhesive 200-nm nanoparticles. This work provides an accurate measurement of the pore structure of fresh, hydrated ex vivo CVM and demonstrates that mucoadhesion, rather than steric obstruction, may be a critical protective mechanism against a major sexually transmitted virus and perhaps other viruses.

Biochemical factors modulating female genital sexual arousal physiology.

INTRODUCTION: Female genital sexual arousal responses are complex neurophysiological processes consisting of central and peripheral components that occur following sexual stimulation. The peripheral responses in sexual arousal include genital vasocongestion, engorgement and lubrication resulting from a surge of vaginal and clitoral blood flow. These hemodynamic events are mediated by a host of neurotransmitters and vasoactive agents. AIM: To discuss the role of various biochemical factors modulating female genital sexual arousal responses. METHODS: A comprehensive literature review was conducted using the PubMed database and citations were selected, based on topical relevance, and examined for study methodology and major findings. MAIN OUTCOME MEASURES: Data from peer-reviewed publications. RESULTS: Adrenergic as well as non-adrenergic non-cholinergic neurotransmitters play an important role in regulating genital physiological responses by mediating vascular and non-vascular smooth muscle contractility. Vasoactive peptides and neuropeptides also modulate genital sexual responses by regulating vascular and non-vascular smooth muscle cells and epithelial function. The endocrine milieu, particularly sex steroid hormones, is critical in the maintenance of tissue structure and function. Reduced levels of estrogens and androgen are associated with dramatic alterations in genital tissue structure, including the nerve network, as well as the response to physiological modulators. Furthermore, estrogen and androgen deficiency is associated with reduced expression of sex steroid receptors and most importantly with attenuated genital blood flow and lubrication in response to pelvic nerve stimulation. CONCLUSIONS: This article provides an integrated framework describing the physiological and molecular basis of various pathophysiological conditions associated with female genital sexual arousal dysfunction.

Assessing heterogeneity in menstrual cycles by means of a multilevel latent class approach.

In this paper, we study the problem of heterogeneity in cervical mucus hydration at different times relative to the mucus peak both between cycles and women, specifying and estimating appropriate multilevel latent class models for longitudinal data. We estimate multilevel and growth latent class models which classify women on the basis of the evolution of cervical mucus characteristics observed over the fertile period of each menstrual cycle taking into account that we observe a different number of cycles per woman and correlation over time between consecutive observations. The effect of potential covariates on mucus evolution patterns is as well evaluated. Results confirm the existence of heterogeneity in mucus evolution between cycles and women. Moreover, an important significant effect of a woman's age is found.

The cervical mucus plug: structured review of the literature.

The cervical mucus plug is a large, complex structure within the cervical canal that is shed shortly before or during labor. We propose that the cervical mucus plug fulfills critical 'gate-keeper' functions based on its physical and immunologic properties, which help prevent ascending infection and preterm labor. The viscoelastic properties of the cervical mucus plug are determined by mucins (large glycoproteins), which can inhibit viral replication and exclude larger molecules and bacteria by preventing their diffusion through the plug. Furthermore, the innate and adaptive immunological properties of the cervical mucus plug are well suited for arresting bacterial infection by stimulating a robust inflammatory response. A possible association between an impaired gate-keeper function of the cervical mucus plug and preterm birth is discussed.

Cohort comparison of two fertility awareness methods of family planning.

OBJECTIVE: To determine if an electronic hormonal fertility monitor aided method (EHFM) of family planning is more effective than a cervical mucus only method (CMM) in helping couples to avoid pregnancy. STUDY DESIGN: Six hundred twenty-eight women were taught how to avoid pregnancy with either the EHFM (n=313) or the CMM (n = 315). Both methods involved standardized group teaching and individual follow-up. All pregnancies were reviewed and classified by health professionals. Correct use and total unintended pregnancy rates over 12 months of use were determined by survival analysis. Comparisons of unintended pregnancies between the 2 methods were made by use of the Fisher exact test. RESULTS: There were a total of 28 unintended pregnancies with the EFHM and 41 with the CMM. The 12-month correct use pregnancy rate of the monitor-aided method was 2.0%, and the total pregnancy rate was 12.0%. In comparison, the 12-month correct use pregnancy rate of the CMM was 3.0%, and the total pregnancy rate was 23.0%. There was a significant difference in total pregnancies between the 2 groups (p<0.05). CONCLUSION: EFHM is more effective than CMM. Further research is needed to verify the results.

Globular structure of human ovulatory cervical mucus.

Human cervical mucus is a heterogeneous mixture of mucin glycoproteins whose relative concentration changes during the ovulatory phases, thereby producing different mucus aggregation structures that can periodically permit the transit of spermatozoa for fertilization. In preovulatory phase, mucus is arranged in compact fiber-like structures where sperm transit is hindered. Previously, through observations made of fixed and dehydrated samples, a permissive structure in the ovulatory phase was attributed to the larger diameters of pores in the mucus network. Instead, by means of atomic force microscopy, we can show, for the first time, that unfixed ovulatory mucus is composed by floating globules of mucin aggregates. This finding sheds new light on the mechanism that governs spermatozoa transit toward the uterine cavity. In addition, we demonstrate that the switch from globular ovulatory to fibrous preovulatory mucus largely depends on a pH-driven mechanism. Analysis of mucin 5B primary sequence, the main mucin in ovulatory mucus, highlights pH-sensitive domains that are associated to flexible regions prone to drive aggregation. We suggest an involvement of these domains in the fiber-to-globule switch in cervical mucus.