Few data are available on the risk of STDs conferred by sex between women, but transmission risk probably varies by the specific STD and sexual practice (e.g., oral-genital sex, vaginal or anal sex using hands, fingers, or penetrative sex items, and oral-anal sex). Practices involving digital-vaginal or digital-anal contact, particularly with shared penetrative sex items, present a possible means for transmission of infected cervicovaginal secretions. This possibility is most directly supported by reports of metronidazole-resistant trichomoniasis and genotype-concordant HIV transmitted sexually between women who reported these behaviors and by the high prevalence of BV among monogamous WSW. Transmission of HPV can occur with skin-to-skin or skin-to-mucosa contact, which can occur during sex between women. HPV deoxyribonucleic acid (DNA) has been detected through polymerase chain reaction (PCR)-based methods from the cervix, vagina, and vulva in 13%–30% of WSW, and high-and low-grade squamous intraepithelial lesions (SIL) have been detected on Pap tests in WSW who reported no previous sex with men. However, the majority of self-identified WSW (53%–99%) have had sex with men and might continue this practice. Therefore, all women should undergo Pap test screening using current national guidelines, regardless of sexual preference or sexual practices.

HSV-2 genital transmission between female sex partners is probably inefficient, but the relatively frequent practice of orogenital sex among WSW might place them at higher risk for genital infection with HSV-1. This hypothesis is supported by the recognized association between HSV-1 seropositivity and previous number of female partners among WSW. Transmission of syphilis between female sex partners, probably through oral sex, has been reported. Although the rate of transmission of C. trachomatis between women is unknown, WSW who also have sex with men are at risk and should undergo routine screening according to guidelines.