Menstrual Cycle Study

Inclusion: * Adults who are between 18 - 42 years old at enrollment and menstruate * Capable of giving informed consent in Spanish or English * Menstrual cycle lengths between 21- 45 days * Have tracked menstruation for at least 3 menstrual cycles out of the prior 6 months * Willing to wear a wrist-worn wearable device continuously for 6 months * Willing to use an ovulation predictor kit for 6 months * Willing to report vaccine history * Owns a smartphone compatible with the study and has access to wi-fi Exclusion: * A citizen of the European Union or United Kingdom * Trying to conceive during the six-month study period * Have used specific forms of birth control in the 3 months prior to the study or planning on using specific birth control methods during the study duration * Participant has undergone hormonal treatment in the past 3 months or planning to do so during the study * Known history of health-related issues that affect their menstrual cycle, history of pelvic radiation, vasomotor symptoms, endometriosis, fibroids, polyps, ovarian cysts or known history of health-related issues that affect the physiology * Currently (or within the past 3 months) engaged in health impacting behaviors * Have been breastfeeding or pregnant in the past 6 months prior to the study * On medications or taking substances that could affect their menstrual cycle or physiology * Travel frequently such as crossing more than two time zones at least once every 2 weeks * Have a known sleeping disorder or consistently work night shifts