OBJECTIVE: To examine the likelihood of self-reporting a diagnosis for PCOS with the presentation of menstrual irregularity in a diverse, multiethnic population, based on data collected between August 9th, 2017 and October 24th, 2017 for the pilot of the Ovulation and Menstruation (OM) Study at Boston University School of Medicine. BACKGROUND: Polycystic ovary syndrome, or PCOS, is the most common endocrine disorder among reproductive age women. It is typically diagnosed by variable combinations of menstrual irregularity, clinical or biochemical hyperandrogenism, and polycystic ovaries on ultrasound. An alternative is its diagnosis as one of exclusion due to similarities in presentation to other endocrine disorders. As a result, PCOS may often be misdiagnosed and mismanaged in the course of a patient’s care, further exacerbated by a poor understanding of the syndrome, a lack of easily available resources, and patient frustration with clinician interactions. The early identification of key hallmarks of the disorder, such as menstrual irregularity, and awareness of its linkage to PCOS, could lead to early diagnosis and intervention. METHODS: 248 participants enrolled and participated in the Ovulation and Menstruation (OM) Health Study’s as members of its pilot cohort. Inclusion criteria were women ages 18-45 currently experiencing menstrual periods without a history of chemotherapy, radiation, or surgical menopause. Participants completed the relevant sections of the OM Study survey related to demographics, menstrual cycle patterns, and history of PCOS. Demographic questions pertained to the age, race/ethnicity, country of birth, and education levels of the participants. The menstrual cycle questions provided information regarding the age of menarche, length and pattern of menses and the menstrual cycle overall. The questions regarding history of PCOS ascertained the presence of an official or self-diagnosis for PCOS for the participant, and the age at which this was determined. The descriptive measures were presented for comparison before determining the concurrence of the presence of menstrual irregularity and the diagnosis of PCOS across demographic categories and calculating an associated prevalence ratio. RESULTS: Among women reporting a history of menstrual irregularity for 3 months or greater, PCOS was the second-highest self-reported cause for menstrual irregularity, with 20.7% of participants endorsing it as the cause for their irregularity. The presence of menstrual irregularity for 3 or more months was also more likely to be present in concurrence with a clinician diagnosis, or to a lesser extent, a self-diagnosis, for PCOS. Participants were also far more likely to have a clinician diagnosis for PCOS if they were White, US-born, young, or educated. The same applied for the likelihood of a self-diagnosis with the exception of age. CONCLUSIONS: The association between menstrual cycle irregularities and likelihood of being diagnosed with PCOS is supported by the data and appears to be influenced by demographic factors such as race/ethnicity, age, and education.