STUDY QUESTION What is the effect of oestrogen and progesterone at the beginning of the menstrual cycle in delaying entry into the fertile window? SUMMARY ANSWER Both oestrogen and progesterone contribute to a delay in the onset of the fertile window. WHAT IS KNOWN ALREADY Oestrogen enhances cervical mucus secretion while progesterone inhibits it. STUDY DESIGN, SIZE, DURATION Observational study. Daily observation of 220 menstrual cycles contributed by 88 women with no known menstrual cycle disorder. PARTICIPANTS/MATERIALS, SETTING, METHODS Women recorded cervical mucus daily and collected first-morning urine samples for analysis of oestrone-3-glucuronide, pregnanediol-3-alpha-glucuronide (PDG), FHS, and LH. They underwent serial ovarian ultrasound examinations. The main outcome measure was the timing within the cycle of the onset of the fertile window, as identified by the appearance of mucus felt or seen at the vulva. MAIN RESULTS AND THE ROLE OF CHANCE Low oestrogen secretion and persistent progesterone secretion during the first week of the menstrual cycle both negatively affect mucus secretion. Doubling oestrogen approximately doubled the odds of entering the fertile window (OR: 1.82 95% CI=1.23; 2.69). Increasing PDG from below 1.5 to 4 µg/mg creatinine was associated with a 2-fold decrease in the odds of entering the fertile window (OR: 0.51 95% CI=0.31; 0.82). Prolonged progesterone secretion during the first week of the menstrual cycle was also statistically significantly associated with higher LH secretion. Finally, the later onset of the fertile window was associated with statistically significant persistently elevated LH secretion during the luteal phase of the previous menstrual cycle. LIMITATIONS, REASONS FOR CAUTION This post hoc study was conducted to assess the potential impact of residual progesterone secretion at the beginning of the menstrual cycle. It was conducted on an existing data set because of the scarcity of data available to answer the question. Analysis with other datasets with similar hormone results would be useful to confirm these findings. WIDER IMPLICATIONS OF THE FINDINGS This study provides evidence for residual progesterone secretion in the early latency phase of some menstrual cycles, which may delay the onset of the fertile window. This progesterone secretion may be supported by subtly increased LH secretion during the few days before and after the onset of menses, which may relate to follicular waves in the luteal phase. Persistent progesterone secretion should be considered in predicting the onset of the fertile window and in assessing ovulatory dysfunction. STUDY FUNDING/COMPETING INTEREST(S) The authors declare no conflicts of interest. No funding was provided for this secondary data analysis. TRIAL REGISTRATION NUMBER N/A.

中文翻译：

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月经周期早期雌激素和黄体酮对受孕窗口时间的影响。


研究问题 月经周期开始时雌激素和黄体酮对延迟进入受孕窗口有何影响？摘要答案 雌激素和黄体酮都会导致受孕窗口出现延迟。已知的情况雌激素会增强宫颈粘液的分泌，而黄体酮会抑制它。研究设计、规模、持续时间 观察性研究。每日观察 88 名没有已知月经周期紊乱的女性的 220 个月经周期。参与者/材料、环境、方法 女性每天记录宫颈粘液，并收集第一天早上的尿液样本，用于分析雌酮-3-葡萄糖醛酸、孕二醇-3-α-葡萄糖醛酸 (PDG)、FHS 和 LH。他们接受了一系列卵巢超声检查。主要结果指标是受孕窗口开始周期内的时间，通过外阴处感觉到或看到的粘液的出现来识别。主要结果和机会的作用 月经周期第一周的低雌激素分泌和持续的黄体酮分泌都会对粘液分泌产生负面影响。雌激素加倍大约使进入受孕窗口的几率增加一倍（OR：1.82 95% CI=1.23；2.69）。将 PDG 从低于 1.5 增加到 4 µg/mg 肌酐与进入生育窗口的几率降低 2 倍相关（OR：0.51 95% CI=0.31；0.82）。月经周期第一周内黄体酮分泌延长也与较高的 LH 分泌具有统计学显着相关性。最后，受孕窗口的较晚出现与前一个月经周期黄体期 LH 分泌持续升高具有统计学意义相关。 局限性和注意理由 这项事后研究的目的是评估月经周期开始时残余黄体酮分泌的潜在影响。由于缺乏可用来回答该问题的数据，该研究是在现有数据集上进行的。对具有类似激素结果的其他数据集进行分析将有助于证实这些发现。研究结果的更广泛意义 这项研究提供了一些月经周期早期潜伏期残留黄体酮分泌的证据，这可能会延迟受孕窗口的开始。这种黄体酮分泌可能受到月经开始前后几天 LH 分泌轻微增加的支持，这可能与黄体期的卵泡波有关。在预测受孕窗口的开始和评估排卵功能障碍时应考虑持续的黄体酮分泌。研究经费/竞争利益 作者声明不存在利益冲突。没有为二次数据分析提供资金。试用注册号 不适用。