Self-identification of the clinical fertile window and the ovulation period

Objective To assess the sensitivity and specificity of the self-identified fertile window. Design Observational study. Setting Not applicable. Patient(s) A total of 107 women. Intervention(s) Women recorded cervical mucus observation and basal body temperature daily while undergoing daily ovarian ultrasound. Main Outcome Measure(s) The biological fertile window, defined as the 6 days up to and including the day of ovulation; and the 2-day ovulation window, defined as the day before and the day of ovulation. Result(s) The self-identification of the biological fertile window by the observation of any type of cervical mucus provides 100% sensitivity but poor specificity, yielding a clinical fertile window of 11 days. However, the identification of the biological fertile window by peak mucus (defined as clear, slippery, or stretchy mucus related to estrogen) yielded 96% sensitivity and improved specificity. The appearance of the peak mucus preceded the biological fertile window in less than 10% of the cycles. Likewise, this type of mucus identified the ovulation window with 88% sensitivity. Conclusion(s) These results suggest that, when perceived accurately, more accurate clinical self-detection of the fertile window can be obtained by identification of peak mucus. This may improve efforts to focus intercourse in the fertile phase for couples with fertility concerns.