HIV acquisition during pregnancy and breastfeeding significantly contributes toward paediatric HIV infection; however, little is known about risk behaviours in HIV-uninfected pregnant and postpartum women. We conducted twenty-six in-depth-interviews between July and December 2016 using a semi-structured interview guide among HIV-uninfected pregnant and recently postpartum women at-risk of HIV acquisition (defined as reporting ≥1 of the following: partner's serostatus unknown or HIV-infected, recent condomless sex in pregnancy, and/or alcohol use during pregnancy) who attended primary healthcare services. Our study contextualizes factors related to risky sexual behaviours during pregnancy and postpartum periods and assesses knowledge and hypothetical acceptability of pre-exposure prophylaxis (PrEP) in pregnancy. Translated and transcribed data were coded and analysed by three researchers using a thematic analysis approach. In interviews with HIV-uninfected pregnant/postpartum women at-risk of HIV acquisition, we identified common themes associated with sexual risk behaviours during pregnancy, including: lack of control over decisions in sex and condom use in pregnancy, low perceived risk (e.g. beliefs that their partner has the same HIV-negative serostatus), and socio-cultural beliefs around condom use during pregnancy (e.g. contact with sperm is essential for baby's development). PrEP knowledge was low among HIV-uninfected pregnant and breastfeeding women, and potential acceptability was good, though primary concerns were around the potential impact on the infant. While mothers presented a clear desire to protect themselves from HIV acquisition once pregnant, they also reported lack of control, and socio-cultural beliefs, like sex is good for the baby, that increased their risk of seroconversion. Mothers had limited PrEP awareness but reported hypothetical willingness to use PrEP because of concerns over HIV acquisition and onward mother to child transmission.