Objective Sex during bleeding is a risk factor for sexually transmitted infection (STI) and other bloodborne viruses, including HIV. We examined daily predictors of adolescent women's male condom use during bleeding-associated vaginal sex.

Methods Adolescent females (N=387; 14–17 years) were recruited from primary care clinics for a longitudinal cohort study of STIs and sexual behaviour. Data were daily partner-specific sexual diaries; generalised estimating equation logistic regression assessed the likelihood of condom use during bleeding-associated vaginal sex.

Results Less than 30% of bleeding-associated vaginal sex events were condom protected. Condom use during these events was less likely with younger age, higher partner support, higher partner negativity or past week bleeding-associated sex with a given partner; condom use was more likely with high individual mood and past week condom use during bleeding-associated vaginal sex with a given partner.

Conclusions Low condom rates during bleeding-associated vaginal sex can increase STI and bloodborne virus risk. Providers should consider integrating partner-specific and behavioural factors when they deliver sexual health messages to young women.