Sexual Health of US Transgender Boys, Nonbinary Youth, and Cisgender Girls.

Importance: Research documenting the pregnancy experiences of transgender boys and nonbinary youth assigned female at birth (AFAB) in the US is lacking. Objective: To examine AFAB youth sexual health indicators by gender. Design, Setting, Participants: Self-reported data were collected cross-sectionally from 2018 through 2020. Initial analyses were conducted in 2023 and analyses were finalized in September 2024. The study took place online, across the 50 US states and Washington, DC. Eligible participants were 14 to 16 years old, read English, and had internet access. Main Outcome: Sexual health (ie, self-reported pregnancy and sexually transmitted infections [STIs] lifetime prevalence, condom use, and use of other forms of birth control at last penile-vaginal or penile-anal sex). Results: Based on weighted data (sample sizes are unweighted), 2109 cisgender girls, 348 transgender boys, and 458 nonbinary AFAB youth were included in analyses. There were 44 transgender boys (14%; 95% CI, 9.4-20.1; P = .24), 67 AFAB nonbinary youth (14%; 95% CI, 10.8-18.8; P = .18), and 397 cisgender girls (18%; 95% CI, 16.0-19.7) who reported ever having penile-vaginal sex. Rates for penile-anal sex were also similar by gender (4% to 6%). Lifetime pregnancy rates were higher for transgender boys (5 [9%]; 95% CI, 2.7-27.1; P = .23) than cisgender (18 [4%]; 95% CI, 2.5-7.1) girls, although not statistically significantly so. Pregnancy rates were similar for AFAB nonbinary youth (5 [5%]; 95% CI, 1.9-13.3; P = .73) compared with cisgender girls. Lifetime STI rates were universally low for all AFAB youth (0.5% to 2.0%). Mean age at first penile-vaginal sex was lower for AFAB nonbinary youth (mean age, 13.6 years; SE, 0.4; P = .003) and transgender boys (mean age, 13.9 years; SE, 0.3; P = .06) compared with cisgender girls (mean age, 14.4 years; SE, 0.1). Condom use at last penile-anal or penile-vaginal sex for transgender boys (24 [16%]; 95% CI, 9.5-27.0; P < .001) and AFAB nonbinary youth (33 [24%]; 95% CI, 16.4-34.2; P < .001) was half that of cisgender girls (245 [49%]; 95% CI, 44.1-54.2). Use of birth control other than condoms at last sex was lower for AFAB nonbinary youth (18 [28%]; 95% CI, 16.2-44.5; P = .14), but similar for transgender boys (20 [42%]; 95% CI, 23.4-62.4; P = .69) compared with cisgender girls (167 [44%]; 95% CI, 38.6-50.0). Conclusion and Relevance: In this cross-sectional study of sexual health among AFAB youth with a diversity of gender identities, transgender boys were more likely, and nonbinary youth, similarly likely, as cisgender girls to be pregnant during adolescence. Even though overall rates of penile-vaginal sex were similar for transgender boys and AFAB nonbinary youth compared with cisgender girls, half as many transgender boys and AFAB nonbinary youth who had this type of sex used a condom at last sex compared with cisgender girls. As with cisgender girls, transgender boys and AFAB nonbinary youth need to be engaged in affirming and inclusive sexual health education.