In pregnant women, where do parasites accumulate?

• A. Intervillous space of placenta
• B. Decidua basalis
• C. Fetal circulation
• D. Umbilical cord

Answer: (A)

In pregnancy, the placenta serves as the main interface between maternal blood and the developing fetus, and many parasites that are circulating in the mother tend to accumulate in the placental tissue where maternal blood pools. This is the intervillous space, the area surrounding the fetal chorionic villi filled with maternal blood. In placental malaria, for example, Plasmodium falciparum–infected red blood cells adhere to placental tissue and build up in this intervillous space, causing inflammation and impaired placental function. The decidua basalis is maternal tissue at the attachment site but isn’t the typical reservoir for parasite sequestration. The fetal circulation and umbilical cord are part of the fetus’s own blood vessels, not the site where maternal parasites accumulate.