Ecological comparison of the risks of mother-to-child transmission and clinical manifestations of congenital toxoplasmosis according to prenatal treatment protocol.

We compared the relative risks of mother-to-child transmission of Toxoplasma gondii and clinical manifestations due to congenital toxoplasmosis associated with intensive prenatal treatment in Lyon and Austria, short term treatment in 51% of Dutch women, and no treatment in Danish women. For each cohort, relative risks were standardized for gestation at seroconversion. In total, 856 mother-child pairs were studied: 549 in Lyon, 133 in Austria, 123 in Denmark and 51 in The Netherlands. The relative risk for mother-to-child transmission compared to Lyon was 1.24 (95% CI: 0.88, 1.59) in Austria; 0.59 (0.41, 0.81) in Denmark; and 0.65 (0.37, 1.01) in The Netherlands. Relative risks for clinical manifestations compared with Lyon (adjusted for follow-up to age 3 years) were: Austria 0.19 (0.04, 0.51); Denmark 0.60 (0.13, 1.08); and The Netherlands 1.46 (0.51, 2.72). There was no clear evidence that the risk of transmission or of clinical manifestations was lowest in centres with the most intensive prenatal treatment.