BackgroundThe HIV risk increases during pregnancy. The elevated risk of HIV acquisition in pregnant women may be explained by behavioural and other factors. The aim of this study was to assess sexual HIV risk behaviour and its associated factors among pregnant women in Mpumalanga, South Africa.MethodsA cross-sectional study was conducted among 1 502 pregnant women (age range 18–47 years, mean age 26.6 years, standard deviation (SD) 6.1, and the mean gestational age was 6.5 months (SD 1.6). Antenatal women were selected, using systematic sampling from 63 primary care clinics and community health centres in Nkangala District. Data were collected by using a structured questionnaire and multivariate logistic regression analysis was used.ResultsThe majority (63%) of the participants had never used a condom with their primary sexual partner in the past 3 months, 60% were not aware of the HIV status of their sexual partner, 7.6% had a casual sexual partner in the past 3 months, 20% had two or more sexual partners in the past 12 months and 17.3% reported to have been diagnosed with a sexually transmitted infection (STI) (other than HIV) in the past 12 months. The various HIV risk behaviours were predicted, by being single and alcohol use for multiple sexual partners; by fewer antenatal visits, being HIV negative and not having used alcohol for lack of condom use; by being HIV positive, having experienced physical partner violence and psychological distress for having been diagnosed with a sexually transmitted infection (other than HIV); and by lower education, unplanned pregnancy, non-antenatal care attendance by expectant father, the belief that antiretrovirals can cure HIV and being HIV positive for having a partner with HIV positve or unknown status.ConclusionHigh levels of sexual HIV risk behaviour were found during pregnancy. Pregnant women need to be informed of their increased risk of HIV and the importance of sexual HIV risk reduction including the use of condoms throughout pregnancy.