The study was aimed at estimating the prevalence of infection with and the genotype of hepatitis C virus (HCV), and to determine the extent of underreporting of HCV cases. A total of 115,386 pregnant women seen by the Program for Protection of Pregnancy [Programa Estadual de Proteção à Gestante] of the state of Mato Grosso do Sul, Central-Western Brazil, were tested for anti-HCV antibodies between 2005 and 2007. Prevalence of HCV infection was 1.07 cases per thousand. Positive samples were tested for HCV RNA and genotyped. Genotype 1 was detected in 73% of samples, genotype 3 in 24.3%, and genotype 2 in 2.7%. Underreporting of hepatitis C cases was 35.5%.