Introduction In endemic countries, Hepatitis B virus (HBV) infection occurs mainly during infancy and early childhood, with vertical transmission from an infected mother being a major route of infection. This study aimed at identifying the prevalence and sexual behavioural risk factors for HBV infection among pregnant women in Ibadan, Nigeria.

Methods A cross-sectional study was done at the antenatal clinic of the University College Hospital Ibadan. One hundred and eighty pregnant women were recruited over a six month period, and their serum was tested for Hepatitis B surface antigen (HBsAg) (BIORAD FRANCE) using third generation ELISA and HIV-1 and 2, using Uni-Gold Recombigen and ALERE determine. Positive HBsAg samples were tested for Hepatitis B envelope antigen (HBeAg), antibody (HBeAb) and Hepatitis B core antibody (HBcAb) (DIAPRO Italy) while serum HBV DNA was detected using PCR. Data were obtained using questionnaires and analysed using SPSS-20

Results The seroprevalence of HBsAg was 8.3% out of which 26.7% were positive for HBeAg, 53.3% had HBeAb, 20% had neither HBeAg nor HBeAb, 100% had total HBcAb and 86.7% had HBV DNA in their serum. A co-infection rate (HBV/HIV) of 26.7% was observed. The mean age was 32.1 years, the highest HBV infection rate occurred in 25–29 year age group. Multiple sexual partners (OR- 3.987, P- value=0.026), early age at sexual debut (OR −11.996, P- value=0.022) were independent risk factors for HBV infection.

Conclusion The result of this study brings to light the high prevalence and high infectivity rate of chronic HBV virus infection among women of child bearing age in Nigeria. Thus, there is a dire need for routine screening for all pregnant women during antenatal care, immunoprophylaxis for exposed newborns and surveillance for those with chronic infection. The socio-demographic and risky sexual behavioural characteristics found to be predictors of HBV infection should be considered when developing strategies towards effective sexual health promotion campaign and health education programs on prevention and control measures.