Patterns of Sexual Practices, Sexually Transmitted Infections and Other Genital Infections in Women Who Have Sex with Women Only (WSWO), Women Who Have Sex with Men Only (WSMO) and Women Who Have Sex with Men and Women (WSMW): Findings from a Sexual Health Clinic in Melbourne, Australia, 2011-2019.

Despite rises in sexually transmitted infection (STI) notifications among Australian women in the last decade, limited STI surveillance data exist specifically for women who have sex with women. This study aimed to compare differences in sexual practices and positivity for STIs and other genital infections among women who have sex with men only (WSMO), women who have sex with women only (WSWO), and women who have sex with men and women (WSMW), and whether these changed over time. In this retrospective repeated cross-sectional study, women attending the Melbourne Sexual Health Centre for the first time between 2011 and 2019 were categorized as "WSMW," "WSWO," or "WSMO" according to self-reported sexual practices in the previous 12 months. Demographic information, sexual practices, and positivity for STIs and other genital infections were compared between the three groups and over time. A total of 36,147 women (2618 WSMW, 534 WSWO, and 32,995 WSMO) were included. WSMW reported more sexual partners (median = 6; IQR = 4-10) than WSMO (median = 3; IQR = 2-5) and WSWO (median = 2; IQR = 1-4) (p < .001). A higher proportion of WSMW always used condoms with casual male partners compared to WSMO (20.4% vs 15.9%; p < .001). The proportion of women who always used condoms with casual male partners decreased over time in WSMO, (19.9% in 2011 to 15.2% in 2019, p < .001) but not in WSMW. Bacterial vaginosis was more common in WSWO (14.8%) than in WSMW (11.8%) and WSMO (7.7%) (p < .001). Chlamydia was more common in WSMO (9.3%) than in WSMW (6.6%) and WSWO (1.2%) (p < .001). Syphilis was more common in WSMO (1.0%) than in WSMW (0.3%) and WSWO (0.0%) (p = .004). Over time, chlamydia positivity in WSWO increased (from 0.0% to 2.7%, p = .014), and syphilis positivity in WSMW increased (from 0.0% to 0.7%, p = .028); however, positivity of these STIs did not change in other groups. Sexual practices and positivity for STIs and other genital infections differed according to the sex of women's partners in the previous 12 months. Knowledge of these differences is important to account for future changes in STI trends that may occur in these subpopulations.