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

• Published in: Human reproduction open 2022-09, Vol.2022 (4), p.1-hoac039
• Main Authors: Najmabadi, S, Schliep, K C, Simonsen, S E, Porucznik, C A, Egger, M J, Stanford, J B
• Format: Article
• Language: English
• Subjects: Fertility, Human; Health aspects; Menstrual cycle; Original; Sexual intercourse
• ISSN: 2399-3529; 2399-3529
• DOI: 10.1093/hropen/hoac039

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 2 days of cervical fluid with estrogen-stimulated qualities. WHAT IS KNOWN ALREADY Human females are spontaneous ovulators, experiencing an LH 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-day 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 centers 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 2564 cycles of 530 women, followed for up to 1 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 1 year, yielding 2564 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 ovul