Toxoplasmosis causes complications during pregnancy that have serious effects on fetal development. Thus far, toxocariasis has been reported to spread only via vertical transmission. Nonetheless, the population of pregnant women is also exposed to this infection. Co-infection with both Toxoplasma gondii and Toxocara spp. has been reported in children, but there are no reports of co-infection in the population of pregnant women. The aim of this study was to determine the prevalence of co-infection with T. gondii and Toxocara spp. in pregnant women at a university hospital in southern Brazil, and to identify the risk factors associated with infection by both parasites. Two hundred pregnant women were tested for the presence of anti-T. gondii and anti-Toxocara spp. antibodies and were asked to complete an epidemiological questionnaire. In this study, the co-infection rate observed in the total population of pregnant women was 8%. In addition, women with a positive result for a serology test for Toxocara spp. were at increased risk of infection by T. gondii (P = 0.019). Co-infection with both parasites in pregnant women was associated with low birth weights in neonates. The similar modes of transmission of both parasites could explain the co-infection. Only a few previous studies have investigated this phenomenon. The findings of the present study emphasize the importance of serological diagnosis during prenatal care and further research in this area to identify risk factors associated with this co-infection, and the possible implications of this co-infection during pregnancy and on the health of newborns.