Fertility Awareness Based Methods (FABMs), such as calendar tracking, basal body temperature (BBT), and monitoring cervical mucus, are widely used but may have limitations in accurately detecting the complete fertility window. Serum hormone measurements and transvaginal ultrasound are more accurate at determining time of ovulation and fertile window, but are costly and inconvenient. Urine-based luteinizing hormone (LH) tests offer improvement. However, LH surge typically occurs 24 to 36 hours prior to ovulation, only capturing the later portion of the fertile window.

A novel approach involves using electrical impedance to track compositional changes in cervical mucus, providing real-time, at-home data. The Kegg device (Lady Technologies Inc, San Francisco, CA, USA) is an intravaginal device that measures cervical mucus impedance to monitor fertility status. Previous studies show it has higher sensitivity, specificity, and accuracy compared to BBT alone in determining the ovulation window. This method offers a cost-effective and practical alternative for at-home fertility tracking.

The objectives of this study are to:

1. evaluate the association between Kegg electrical impedance readings and cervical mucus observations with regard to determining fertility status; and
2. compare the accuracy of Kegg electrical impedance readings with hormone urine strips in identifying the complete fertile window determined by cervical mucus observations.

Inclusion Criteria:

1. Biological female
2. Age between 18-40 years old
3. Participant has provided signed informed consent
4. Completed cervical mucus observation training
5. Owns and uses daily a smart device meeting the following requirement: Apple iPad or iPhone running iOS 13 or newer, or Apple Watch running WatchOS 6.0 or newer, or Android operating system of 6.0 or newer
6. Has readily accessible internet
7. Legal residents of the continental United States, excluding Alaska and Hawaii.

Exclusion Criteria:

1. Participant is unable to read and understand English
2. Postmenopausal women
3. Women with hysterectomy
4. Pregnancy
5. Hormonal or intrauterine contraceptives or other hormone use prior to start of study enrollment [No oral hormonal contraceptives or other hormones for at least one month, no implantable contraceptives or hormonal or non-hormonal intrauterine device for at least two months (~2 cycles), no injectable hormonal contraceptives or other hormones in past 9 months from the most recent injection and resumption of regular menstrual cycles](streamdown:incomplete-link)

Women who meet the eligibility criteria