We assessed recent trends in hepatitis C virus (HCV) prevalence in pregnant women with HIV using data from a large national study. Based on 1240 pregnancies, we observed a 3·4-fold decline in HCV seroprevalence in pregnant women with HIV between 2001 (29·3%) and 2008 (8·6%). This decline was the net result of two components: a progressively declining HCV seroprevalence in non-African women (from 35·7% in 2001 to 16·7% in 2008), sustained by a parallel reduction in history of injecting drug use (IDU) in this population, and a significantly growing presence (from 21·2% in 2001 to 48·6% in 2008) of women of African origin, at very low risk of being HCV-infected [average HCV prevalence 1%, adjusted odds ratio (aOR) for HCV 0·09, 95% CI 0·03–0·29]. Previous IDU was the stronger determinant of HCV co-infection in pregnant women with HIV (aOR 30·9, 95% CI 18·8–51·1). The observed trend is expected to translate into a reduced number of cases of vertical HCV transmission.