Background The trafficking of women and girls for sexual exploitation is an internationally recognised form of gender-based violence, and is thought to confer unique sexual and reproductive health vulnerabilities. To date, little research has compared sexual risk or health outcomes among female sex workers (FSWs) on the basis of experiences of sex trafficking.

Aim To compare experiences of sexual risk and sexual and reproductive health outcomes among FSWs on the basis of experiences of trafficking as an entry mechanism to sex work.

Methods Data from a national sample of FSWs in Thailand (n=815) was used to assess (a) the prevalence of sex trafficking as an entry mechanism into sex work and (b) associations of sex trafficking with sexual risk and health outcomes.

Results Approximately 10% of FSWs met criteria for trafficking as an entry mechanism to sex work. Compared with their non-trafficked counterparts, sex-trafficked FSWs were more likely to have experienced sexual violence at initiation to sex work (adjusted risk ratio (ARR) 2.29, 95% CI 1.11 to 4.72), recent workplace violence or mistreatment (ARR 1.38, 95% CI 1.13 to 1.67), recent condom failure (ARR 1.80, 95% CI 1.15 to 2.80), condom non-use (ARR 3.35, 95% CI 1.49 to 7.52) and abortion (ARR 2.83, 95% CI 1.48 to 5.39).

Discussion Both the prevalence of sex trafficking as an entry mechanism to sex work and the threats to sexual and reproductive health observed on the basis of trafficking status show the need for comprehensive efforts to identify and support this vulnerable population. Moreover, existing STI/HIV-prevention programming may be stymied by the limited condom-use capacity and high levels of violence observed among those trafficked into sex work.