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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雌激素和孕激素对早期月经周期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孕激素对延迟进入受孕窗口有什么影响？摘要 答案 雌激素和黄体酮都会导致受孕窗口开始的延迟。已知的是：雌激素增强宫颈粘液分泌，而黄体酮抑制它。研究设计、规模、持续时间 观察性研究。每天观察 220 个月经周期，由 88 名没有已知月经周期障碍的女性贡献。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-葡萄糖醛酸苷、孕二醇-3-α-葡萄糖醛酸苷 （PDG） 、FHS 和 LH。他们接受了一系列卵巢超声检查。主要结局指标是受孕窗口开始周期内的时间，通过外阴感觉或看到的粘液外观来确定。主要结果和机会的作用 月经周期第一周雌激素分泌低和孕激素持续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 μg/mg 肌酐增加到 4 μg/mg 肌酐与进入受孕窗口的几率降低 2 倍相关 （OR： 0.51 95% CI=0.31; 0.82）。月经周期第一周孕酮分泌延长与 LH 分泌增加也有统计学意义相关。最后，受孕窗口的较晚开始与前一次月经周期的黄体期 LH 分泌持续升高具有统计学意义相关。 局限性，谨慎的原因 进行这项事后研究是为了评估月经周期开始时残留黄体酮分泌的潜在影响。由于可用于回答这个问题的数据稀缺，它是在现有数据集上进行的。使用具有类似激素结果的其他数据集进行分析将有助于确认这些发现。研究结果的更广泛意义 本研究为某些月经周期的早期潜伏期残留黄体酮分泌提供了证据，这可能会延迟受孕窗口的开始。在月经开始前后的几天内，LH 分泌略微增加可能支持这种孕酮分泌，这可能与黄体期的卵泡波有关。在预测受孕期窗口的开始和评估排卵功能障碍时，应考虑持续的孕激素分泌。研究经费/利益争夺 作者声明没有利益冲突。没有为这项二次数据分析提供资金。试验注册号 N/A。