Congenital toxoplasmosis in twins: a report of fourteen consecutive cases and a comparison with published data

Background. The combined influence of congenital toxoplasmosis and twin pregnancy on the duration of gestation has not been previously examined. Similarly little is known about the influence of genetic factors on the clinical course of this disease. The present study addresses these issues. Patients and methods. Fourteen consecutive twin pairs born of mothers with Toxoplasma seroconversion during pregnancy were monitored after birth and during childhood, and the relevant data were compared with those already documented for similar cases. Results. The presumed time of gestation at which women became infected was earlier in noninfected than in infected twins (P = 0.007). Congenital infection did not influence the duration of pregnancy either in our own cases [36.2 +/- 4.3 weeks for noninfected children and 37.4 +/- 1.8 weeks for infected ones (P = 0.45)] or in previously published ones [35.4 +/- 3.6 weeks (P = 0.69)]. The infection status was identical for monozygotic twins (with one exception) but different for dizygotic ones (19 of 20 vs. 35 of 45 cases). The clinical course through childhood corresponded more closely for monozygotic twins than for dizygotic ones [17 of 20 vs. 20 of 45 cases (P = 0.007)]. Conclusion. Twin pregnancy is not a risk factor either for premature birth or for Toxoplasma infection in contaminated twins. The closely corresponding infection status between monozygotic twins highlights the crucial role played by the placenta in disease transmission. However, the substantial proportion of discrepant clinical courses suggests that other, as yet unknown, factors may be involved.