OVA cohort. 

The OVA cohort included 921 ovulatory women not seeking fertility treatment. Subjects were a part of a community-based cohort, the Ovarian Aging study (16), a prospective, observational study designed to investigate reproductive aging. OVA participants were evaluated at University of California, San Francisco. Participants were recruited between 2006 and 2010 from a sampling frame of all age-eligible female members of the Kaiser Permanente of Northern California Health Plan, within a reasonable travel distance to the research center. Kaiser Permanente is an integrated healthcare delivery system covering 30% of the regional population. Inclusion criteria for the OVA population included regular menses at 22- to 35-day intervals and self-identification in 1 of 4 racial/ethnic groups categorized as Caucasian, Asian, Hispanic, or African American. Women reporting multiethnic origin were not enrolled.

Exclusion criteria for the OVA cohort included estrogen- or progestin-containing medication use in the 3 months before enrollment, history of endometriosis, or any history of uterine or ovarian surgery. Further information regarding the study design and methodology for OVA have been previously published (16, 37).