Background
Previous research on polycystic ovary syndrome (PCOS) and endometriosis has not identified significant differences by sexual orientation. However, these studies were limited to small samples or those from fertility clinics.

Methods
We analyzed cross-sectional survey data from the National College Health Assessment administered between Fall 2019 and Spring 2020. Our analytic sample included 47,727 cisgender women aged 18-25. Prevalence ratios (PR) for PCOS and endometriosis by sexual orientation were estimated using log-binomial regression models adjusted for region, age, race/ethnicity, and parental education (a marker of socioeconomic status).

Results
PCOS diagnoses were more common among asexual (PR=1.67; 95%CI:1.15-2.44), bisexual/pansexual (PR=1.50; 95%CI: 1.33-1.69), lesbian/gay (PR=1.52; 95%CI:1.17-1.97), and queer (PR=1.58; 95%CI:1.12-2.24) women than heterosexual women. Compared to heterosexual women, endometriosis diagnoses were more common among bisexual/pansexual (PR=1.54; 95%CI:1.30-1.83), lesbian/gay (PR=1.72; 95%CI=1.19-2.47), and queer (PR=2.19; 95%CI: 1.39-3.43) women. Heterosexual women with same-gender partners did not significantly differ from heterosexual women without same-gender partners for either diagnosis. Sexual minorities were as likely as heterosexuals to have received past-year care for their diagnoses.

Discussion
PCOS and endometriosis diagnoses were more common among sexual minority than heterosexual women. Our findings may underestimate the disparities in PCOS and endometriosis prevalence if these conditions are underdiagnosed among sexual minorities due to differences in healthcare access and use. Further, our findings may contradict previous research due to selection bias induced by using fertility-clinic based samples or low power in previous studies. Additional research using non-clinic-based samples is needed to confirm our findings.