Characteristics of menstrual cycles with or without intercourse in women with no known subfertility

Abstract

STUDY QUESTION Does sexual intercourse enhance the cycle fecundability in women without known subfertility? SUMMARY ANSWER Sexual intercourse (regardless of timing during the cycle) was associated with cycle characteristics suggesting higher fecundability, including longer luteal phase, less premenstrual spotting, and more than two days of cervical fluid with estrogen-stimulated qualities. WHAT IS KNOWN ALREADY Human females are spontaneous ovulators, experiencing a luteinizing hormone surge and ovulation cyclically, independent of copulation. Natural conception requires intercourse to occur during the fertile window of a woman’s menstrual cycle, i.e., the 6-days interval ending on the day of ovulation. However, most women with normal fecundity do not ovulate on day 14, thus the timing of the hypothetical fertile window varies within and between women. This variability is influenced by age and parity and other known or unknown elements. While the impact of sexual intercourse around the time of implantation on the probability of achieving a pregnancy has been discussed by some researchers, there are limited data regarding how sexual intercourse may influence ovulation occurrence and menstrual cycle characteristics in humans. STUDY DESIGN, SIZE, DURATION This study is a pooled analysis of three cohorts of women, enrolled at Creighton Model FertilityCare centres in the USA and Canada: “Creighton Model MultiCenter Fecundability Study” (CMFS: retrospective cohort, 1990–1996), “Time to Pregnancy in Normal Fertility” (TTP: randomized trial, 2003–2006), and “Creighton Model Effectiveness, Intentions, and Behaviors Assessment” (CEIBA: prospective cohort, 2009–2013). We evaluated cycle phase lengths, bleeding and cervical mucus patterns and estimated the fertile window in 2,564 cycles of 530 women, followed for up to one year. PARTICIPANTS/MATERIALS, SETTING, METHODS Participants were US or Canadian women aged 18–40 and not pregnant, who were heterosexually active, without known subfertility and not taking exogenous hormones. Most of the women were intending to avoid pregnancy at the start of follow-up. Women recorded daily vaginal bleeding, mucus discharge and sexual intercourse using a standardized protocol and recording system for up to one year, yielding 2,564 cycles available for analysis. The peak day of mucus discharge (generally the last day of cervical fluid with estrogen-stimulated qualities of being clear, stretchy or slippery) was used to identify the estimated day of ovulation, which we considered the last day of the follicular phase in ovulatory cycles. We used linear mixed models to assess continuous cycle parameters including cycle, menses and cycle phase lengths, and generalized linear models using Poisson regression with robust variance to assess dichotomous outcomes such as ovulatory function, short luteal phases, and presence or absence of follicular or luteal bleeding. Cycles were stratified by the presence or absence of any sexual intercourse, while adjusting for women’s parity, age, recent oral contraceptive use and breast feeding. MAIN RESULTS AND THE ROLE OF CHANCE Most women were <30 years of age (75.5%) (median 27, interquartile range 24–29), non-Hispanic White (88.1%), with high socioeconomic indicators, and nulliparous (70.9%). Cycles with no sexual intercourse compared to cycles with at least one day of sexual intercourse were shorter (29.1 days (95% confidence interval 27.6, 30.7) versus 30.1 days (95% confidence interval 28.7, 31.4)), had shorter luteal phases (10.8 days (95% confidence interval 10.2, 11.5) versus 11.4 days (95% confidence interval 10.9, 12.0)), had a higher probability of luteal phase deficiency (<10 days) (adjusted probability ratio 1.31 (95% confidence interval 1.00, 1.71)), had a higher probability of two days of premenstrual spotting (adjusted probability ratio 2.15 (95% confidence interval 1.09, 4.24)), and a higher probability of having two or fewer days of peak-type (estrogenic) cervical fluid (adjusted probability ratio 1.49 (95% confidence interval 1.03, 2.15)). LIMITATIONS, REASONS FOR CAUTION Our study participants were geographically dispersed but relatively homogeneous in regard to race, ethnicity, income and educational levels, and all had male partners, which may limit the generalizability of the findings. We cannot exclude the possibility of undetected subfertility or related gynaecologic disorders among some of the women, such as undetected endometriosis or polycystic ovary syndrome, which would impact the generalizability of our findings. Acute illness or stressful events might have reduced the likelihood of any intercourse during a cycle, while also altering cycle characteristics. Some cycles in the no intercourse group may have actually had undocumented intercourse or other sexual activity, but this would bias our results towards the null. The Creighton Model FertilityCare System (CrM) discourages use of barrier methods, so we believe that most instances of intercourse involved exposure to semen; however, condoms may have been used in some cycles. Our dataset lacks any information about the occurrence of female orgasm, precluding our ability to evaluate the independent or combined impact of female orgasm on cycle characteristics. WIDER IMPLICATIONS OF THE FINDINGS Sexual activity may change reproductive hormonal patterns, and/or levels of reproductive hormones may influence the likelihood of sexual activity. Future work may help with understanding the extent to which exposure to seminal fluid, and/or female orgasm and/or timing of intercourse could impact menstrual cycle function. In theory, large data sets from women using menstrual and fertility tracking apps could be informative if women can be appropriately incentivized to record intercourse completely. It is also of interest to understand how cycle characteristics may differ in women with gynecological problems or subfertility. STUDY FUNDING/COMPETING INTEREST(S) Funding for the research on the three cohorts analyzed in this study was provided by the Robert Wood Johnson Foundation (Creighton Model MultiCenter Fecundability Study), the Eunice Kennedy Shriver National Institute of Child Health and Human Development (Time to Pregnancy in Normal Fertility), and the Office of Family Planning, Office of Population Affairs, Health and Human Services (Creighton Model Effectiveness, Intentions, and Behaviors Assessment). The authors declare that they have no conflict of interest. TRIAL REGISTRATION NUMBER N/A

Global Menstrual Cycle Symptomatology as Reported by Users of a Menstrual Tracking Mobile Application

“…Our results build on prior work evaluating the menstrual cycle characteristics of women using period tracking apps. The median cycle length, 28.7 days in our study, is consistent with previous studies and period tracking app data 17,[20][21][22][23][24] .…”

“…The copyright holder for this preprint this version posted October 21, 2022. ; https://doi.org/10.1101/2022.10.20.22280407 doi: medRxiv preprint using period tracking apps. The median cycle length, 28.7 days in our study, is consistent with previous studies and period tracking app data 17,[20][21][22][23][24] . Somatic symptoms were reported most frequently, with cramps being the most reported symptom.…”

A comprehensive genome-wide cross-trait analysis of sexual factors and uterine leiomyoma

“…The similar enrichment patterns when partitioning heritability for UL and that of sexual factors further elucidate potential overlapped etiology related to the immune system. A chronically active inflammatory immune system is suggested to be involved in UL formation [ 45 , 46 ], and sexual factors are linked to sex hormones [ 6 , 7 ] which have well-established impacts on immune responses [ 47 ]. Future work is warranted to fully uncover specific pathways that underlie the UL-AFS/NSP biological associations.…”

“…In contrast, sexual factors such as age at first sexual intercourse (AFS) and lifetime number of sexual partners (NSP) receive little empirical attention, even with a decrease in AFS and an increase in NSP being observed in many contemporary societies [3][4][5]. In addition to impacting ovulation and hormonal concentrations [6,7], sexual factors may expose participants to infectious agents in the uterus [8,9]. Therefore, low AFS or high NSP may correlate with alterations in sex hormones and/or an increased susceptibility to uterine infections, both of which have previously been hypothesized to play an etiologic role in UL pathogenesis [10][11][12][13][14].…”

The Duration of Menstrual Blood Loss: Historical to Current Understanding

“…In a study that included 581 women who contributed 3324 cycles, the majority were <30 years of age (74.5%), non-Hispanic white (88.6%), and nulliparous (70.4%). The mean menses length was 6.2 days (SD = 1.5, range 3-15), and 11.6% of all participants experienced a >3-day difference between the longest and shortest menses length [42]. The study by Park et al reported an average duration of bleeding of 5.6 days; 95.2% reported bleeding between 2 and 7 days and 4.8% reported more than 8 days of bleeding [43].…”