Etiology of Placental Plasmodium falciparum Malaria in African Women.

Plasmodium falciparum parasites causing placental malaria express the VAR2CSA type of the clonally variant antigen family erythrocyte membrane protein 1 (PfEMP1). This enables evasion of preexisting immunity and results in placental accumulation of infected erythrocytes. We present data on seasonal variation in levels of VAR2CSA-specific immunoglobulin G (IgG) and IgG specific for a placental malaria-unrelated PfEMP1 protein among Ghanaian women at their first antenatal visit. Our results indicate that placental malaria does not require recent exposure to infected mosquitoes, in contrast to malaria in general. This has implications for the impact of insecticide-treated bed nets on placental malaria incidence and for antenatal care in woman with preexisting immunity.