Invasive and transovaric transmission of Trypanosoma cruzi: their relationship to congenital transmission of the parasite in Colombia. The epidemiology of the association between Trypanosoma cruzi infection and congenital transmission of the parasite was studied in Colombia. Blood samples and sera were obtained from 1,050 children 1-6 months old and 1,100 matched mothers who had been tested by hemagglutination assay. Congenital transmission of T. cruzi was found in 36 (3.2%) of the children. No correlation was found between the type of congenital transmission and the source of maternal blood, the infecting T. cruzi strain or the duration of gestation. However, the use of oral rehydration solution was more common among children with congenital T. cruzi infection and was associated with a history of neonatal prematurity (chi 2, p < 0.01) and history of maternal T. cruzi infection (p = 0.01). Mothers with no history of T. cruzi infection were associated with a history of the use of oral rehydration solution (chi 2, p < 0.01). An additional finding was that mothers who reported that they had been treated during the last year with meglumine antimoniate were associated with congenital transmission (p < 0.001). The results of this study indicate that in an area of high T. cruzi transmission, congenital transmission of T. cruzi is associated with the mode of delivery and the use of oral rehydration solution. However, the epidemiological risk factors for congenital transmission are different from those found for T. cruzi infection in utero and by oral route. This difference might be due to the presence of the placenta and amniotic membrane as barriers between the mother and the fetus.