Malaric placentas. A quantitative study and clinico-pathological correlations.

A histological and morphometric study was conducted on 372 placentae out of a total 440 delivered in Zanzibar. Fibrin (F), intervillous space (IVS) and Villi (V) relative volumes were determined by the point-counting system and the ratio of syncytium to blood capillaries by the linear intercept method. Parasitemia load and inflammatory reaction were graded semiquantitatively by the use of a 1 mm square grid. Parasitised red cells identified active malaria (AM), the presence of malarial pigment only identified past malaria (PM), and the absence of both characterized non-malarial placentae (NM). AM(17.87%), PM(21.61%) and NM(60.52%) placentae did not vary significantly in weight. Newborns from AM had a significantly lower weight than those from PM and NM. Peripheral and placental parasitemia were not coincident. Placental parasitemia load increased parallel with birthweight. The latter decreased with the increasing severity of the inflammation, particularly with the prevalence of lymphocytes in the IVS. Significantly increased volume of F was found in AM and PM placentae, while no significant variation was noticed in IVS and V volumes. The syncytium/capillaries ratio was significantly increased in AM. We conclude that low birthweight in malaria is linked to IVS inflammation but not to F deposits or parasitemia load. Non-leukotactic lymphokines might play some role. Morphologic aspects bespeak for a less mature placenta than expected and this might represent an adaptive change.