Which of the following infections is NOT a transplacental infection?

The correct answer identifies that syphilis is not traditionally classified as a transplacental infection, while the other options involve infectious agents that can indeed cross the placenta from the mother to the fetus, leading to congenital infections.

Transplacental infections occur when pathogens traverse the placenta during pregnancy, potentially leading to significant fetal complications. Toxoplasmosis, for instance, is caused by the Toxoplasma gondii organism and can cause severe outcomes if contracted during pregnancy. Similarly, the herpes simplex virus can be transmitted through the placenta if the mother has an active infection during delivery.

Group B streptococcus, while it can be a concern during labor and delivery due to the potential of neonatal infection, is typically transmitted during passage through the birth canal rather than via the placenta, which differentiates it from true transplacental infections.

Syphilis, on the other hand, although it can affect the fetus and lead to congenital syphilis, does so more directly through the maternal bloodstream rather than through the placental route typically recognized for transplacental infections. Therefore, classifying syphilis as a transplacental infection is less accurate compared to the other conditions listed, solidifying its distinction in this context.