STUDY QUESTION What is the relative length variance of the luteal phase compared to the follicular phase within healthy, non-smoking, normal-weight, proven normally ovulatory, premenopausal women with normal-length menstrual cycles? SUMMARY ANSWER Prospective 1-year data from 53 premenopausal women with two proven normal-length (21–36 days) and normally ovulatory (≥10 days luteal) menstrual cycles upon enrollment showed that, despite 29% of all cycles having incident ovulatory disturbances, within-woman follicular phase length variances were significantly greater than luteal phase length variances. WHAT IS KNOWN ALREADY Many studies report menstrual cycle variability, yet few describe variability in follicular and luteal phase lengths. Luteal lengths are assumed ‘fixed’ at 13–14 days. Most studies have described follicular and luteal phase variability between-women. STUDY DESIGN, SIZE, DURATION This study was a prospective, 1-year, observational cohort study of relative follicular and luteal phase variability both between and within community-dwelling women with two documented normal-length (21–36 days) and normally ovulatory (≥10 days luteal phase) menstrual cycles prior to enrollment. Eighty-one women enrolled in the study and 66 women completed the 1-year study. This study analyzed data from 53 women with complete data for ≥8 cycles (mean 13). PARTICIPANTS/MATERIALS, SETTING, METHODS Participants were healthy, non-smoking, of normal BMI, ages 21–41 with two documented normal-length (21–36 days) and normally ovulatory (≥10 days luteal phase) menstrual cycles prior to enrollment. Participants recorded first morning temperature, exercise durations, and menstrual cycle/life experiences daily in the Menstrual Cycle Diary. We analyzed 694 cycles utilizing a twice-validated least-squares Quantitative Basal Temperature method to determine follicular and luteal phase lengths. Statistical analysis compared relative follicular and luteal phase variance in ovulatory cycles both between-women and within-woman. Normal-length cycles with short luteal phases or anovulation were considered to have subclinical ovulatory disturbances (SOD). MAIN RESULTS AND THE ROLE OF CHANCE The 1-year overall 53-woman, 676 ovulatory cycle variances for menstrual cycle, follicular, and luteal phase lengths were 10.3, 11.2, and 4.3 days, respectively. Median variances within-woman for cycle, follicular, and luteal lengths were 3.1, 5.2, and 3.0 days, respectively. Menstrual cycles were largely of normal lengths (98%) with an important prevalence of SOD: 55% of women experienced >1 short luteal phase (<10 days) and 17% experienced at least one anovulatory cycle. Within-woman follicular phase length variances were greater than luteal phase length variances (P < 0.001). However, follicular (P = 0.008) and luteal phase length (P = 0.001) variances, without differences in cycle lengths, were greater in women experiencing any anovulatory cycles (n = 8) than in women with entirely normally ovulatory cycles (n = 6). LIMITATIONS, REASONS FOR CAUTION Limitations of this study include the relatively small cohort, that most women were White, initially had a normal BMI, and the original cohort required two normal-length and normally ovulatory menstrual cycles before enrollment. Thus, this cohort’s data underestimated population menstrual cycle phase variances and the prevalence of SOD. WIDER IMPLICATIONS OF THE FINDINGS Our results reinforce previous findings that the follicular phase is more variable than the luteal phase in premenopausal women with normal-length and ovulatory menstrual cycles. However, our study adds to the growing body of evidence that the luteal phase is not predictably 13–14 days long. STUDY FUNDING/COMPETING INTEREST(S) This medical education project of the University of British Columbia was funded by donations to the Centre for Menstrual Cycle and Ovulation Research. The authors do not have any conflicts of interest to disclose. TRIAL REGISTRATION NUMBER N/A.

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预先筛选为月经周期和黄体期长度正常的健康女性卵泡期和黄体期长度女性内部变异性的 1 年前瞻性评估


研究问题 对于健康、不吸烟、体重正常、经证实正常排卵、月经周期正常的绝经前妇女，黄体期与卵泡期的相对长度差异是多少？摘要答案 来自 53 名绝经前妇女的前瞻性 1 年数据，其中两个经证实的月经周期正常（21-36 天）和正常排卵（≥10 天黄体）月经周期表明，尽管所有周期中有 29% 发生排卵障碍，但女性体内卵泡期长度差异显著大于黄体期长度差异。已经知道的 许多研究报告了月经周期的变异性，但很少有研究描述了卵泡和黄体期长度的变异性。假设黄体长度“固定”在 13-14 天。大多数研究描述了女性之间的卵泡期和黄体期差异。研究设计、大小、持续时间 本研究是一项为期 1 年的前瞻性观察性队列研究，研究了社区居民妇女之间和内部的卵泡和黄体期相对变异性，在入组前有两个记录的正常长度（21-36 天）和正常排卵（≥10 天黄体期）月经周期。81 名女性参加了这项研究，66 名女性完成了为期 1 年的研究。本研究分析了 53 名女性的数据，具有 ≥8 个周期的完整数据（平均 13 个）。参与者/材料、设置、方法 参与者健康、不吸烟、BMI 正常，年龄在 21-41 岁之间，入组前有两次记录的正常长度（21-36 天）和正常排卵（≥10 天黄体期）月经周期。参与者每天在月经周期日记中记录第一次早晨的体温、运动持续时间和月经周期/生活经历。 我们使用两次验证的最小二乘定量基础温度方法分析了 694 个周期，以确定卵泡和黄体期长度。统计分析比较了女性和女性内排卵周期的卵泡期和黄体期相对差异。黄体期短或无排卵的正常长度周期被认为具有亚临床排卵障碍 （SOD）。主要结果和机会的作用 1 年总体 53 名女性，676 个排卵周期的月经周期、卵泡和黄体期长度差异分别为 10.3 、 11.2 和 4.3 天。女性体内周期、卵泡和黄体长度的中位方差分别为 3.1 、 5.2 和 3.0 天。月经周期大部分正常 （98%），SOD 患病率很高：55% 的女性经历了 >1 黄体期短（<10 天），17% 的女性经历了至少一个无排卵周期。女性卵泡期长度方差大于黄体期长度方差 （P < 0.001）。然而，在无周期差异的情况下，经历任何无排卵周期的妇女 （n = 8） 的卵泡 （P = 0.008） 和黄体期长度 （P = 0.001） 差异大于完全正常排卵周期的妇女 （n = 6）。局限性，谨慎的原因 本研究的局限性包括相对较小的队列，大多数女性是白人，最初的 BMI 正常，而原始队列在入组前需要两个正常长度且正常排卵的月经周期。因此，该队列的数据低估了人群月经周期阶段方差和 SOD 的患病率。 研究结果的更广泛意义 我们的结果强化了先前的发现，即在月经周期正常且排卵正常的绝经前妇女中，卵泡期比黄体期更具可变性。然而，我们的研究增加了越来越多的证据，表明黄体期无法预测地长达 13-14 天。研究资金/竞争利益 不列颠哥伦比亚大学的这个医学教育项目由对月经周期和排卵研究中心的捐款资助。作者没有任何需要披露的利益冲突。试验注册号 N/A。