Placental Malaria

Abstract

Purpose of review: Placental malaria is the primary mechanism through which malaria in pregnancy causes adverse perinatal outcomes. This review summarizes recent work on the significance, pathogenesis, diagnosis, and prevention of placental malaria.

Recent findings: Placental malaria, characterized by the accumulation of Plasmodium-infected red blood cells in the placental intervillous space, leads to adverse perinatal outcomes such as stillbirth, low birth weight, preterm birth, and small-for-gestational-age neonates. Placental inflammatory responses may be primary drivers of these complications. Associated factors contributing to adverse outcomes include maternal gravidity, timing of perinatal infection, and parasite burden.

Summary: Placental malaria is an important cause of adverse birth outcomes in endemic regions. The main strategy to combat this is intermittent preventative treatment in pregnancy; however, increasing drug resistance threatens the efficacy of this approach. There are studies dissecting the inflammatory response to placental malaria, alternative preventative treatments, and in developing a vaccine for placental malaria.

Keywords: Malaria in pregnancy; Obstetrical outcomes of placental malaria; Pathogenesis of placental malaria; Placental malaria; Plasmodium infection; Prevention of placental malaria.

Fig. 1

Global incidence of P. falciparum. Time-aware mosaic data set showing predicted all-age incidence rate (clinical cases per 1000 population per annum) of Plasmodium falciparum malaria for each year. Colors: one linear scale between rates of zero and 10 cases per 1000 (gray shades) and a second linear scale between 10 and 1000 (colors from purple to yellow). Malaria Atlas Project: WHO Collaborating Centre. Explorer Map - Plasmodium falciparum Incidence. No changes made to the map. Legend represented as is from map. Image located at: https://malariaatlas.org/explorer/#/. Available through open access via the Creative Commons Attribution 3.0 Unported License accessible through: creativecommons.org/licenses/by/3.0/. Disclaimer: Authors of this paper were not involved in the making of this map. This image was made through the Malaria Atlas Project. See open access attribution information above for details on accessing the map

Fig. 2

Histological cross section of chorionic villi. (a) Chorionic villi (CV) have a continuous layer of syncytiotrophoblasts separating fetal and maternal cells. Fetal blood vessels (FBV) are located within the CV whereas maternal red blood cells (RBC) are circulating in the intervillous space (IVS). (b) During placental malaria, infected red blood cells (iRBC) accumulate within the IVS and lead to fibrin deposition (FD) and syncytial knot (SK) formation. Normal light (c) and polarized light (d) microscopy of malaria-infected placenta demonstrating hemozoin (HZ), dark-brown pigment in normal light and red in polarized light, accumulation within iRBC, and maternal intervillous monocyte (MIM)