RT Journal Article SR Electronic T1 Do young women engage in greater sexual risk behaviour with biological fathers of their children? JF Sexually Transmitted Infections JO Sex Transm Infect FD BMJ Publishing Group Ltd SP sextrans-2015-052157 DO 10.1136/sextrans-2015-052157 A1 Michele R Decker A1 Shang-En Chung A1 Jonathan M Ellen A1 Susan G Sherman YR 2015 UL http://sti.bmj.com/content/early/2015/09/21/sextrans-2015-052157.abstract AB Objectives Qualitative research suggests that young women's relationships with the biological fathers of their children (BFRs), known colloquially as ‘baby daddy’ relationships, enable risk for pregnancy and STI/HIV. Our study compared partner characteristics and sexual risk within dyads based on BFR, among a sample of young women in Baltimore, Maryland, USA.Methods We conducted secondary analysis of survey data collected in 2011–2013 from heterosexually experienced youth ages 15–24 in Baltimore, Maryland, USA. Analyses are limited to women with at least one recent (past 6 months) sex partner (n=171 participants, reporting on 271 relationships). Using generalised estimating equations with logit function for correlated binary responses, we evaluate associations of BFR with partner characteristics, sexual risk behaviour and contraceptive non-use.Results At least one BFR partner was reported by 25.2%. Male partners in BFRs were more likely to have been incarcerated or arrested. BFRs were more often characterised by women as ‘main’ versus ‘casual’ partners (adjusted OR (AOR) 3.92, 95% CI 1.19 to 12.9). In adjusted analyses, BFR was associated with condom non-use for vaginal (AOR 12.3, 95% CI 3.92 to 38.7) and anal (AOR 3.32, 95% CI 1.34 to 8.22) intercourse. While BFR was associated with contraceptive non-use (AOR 2.21, 95% CI 1.01 to 4.84), this association attenuated to non-significance after adjusting for partnership type (AOR 2.06, 95% CI 0.91 to 4.67).Conclusions While few differences in BFR partner characteristics emerged, significantly greater risk for unprotected intercourse was identified within BFR relationships. Findings suggest that the relationship context of a shared child heightens sexual risk for the young women most affected by STI.