Placental Pathology

After receiving the placentas fresh from the labor and delivery ward, the pathologists assessed the membranes, measured the cord, and documented its insertion, length, diameter, and appearance. They also weighed and measured the disc, after removing the cord and membranes, and again documented the appearance of the disc with the fetal and maternal surface. For microscopy, the following sections were taken: two cross-sections of the cord, one membrane roll, and sections of the central placental disc, and in areas of any lesions identified. The sections for histology were fixed in 10% buffered formalin and processed overnight for histology and stained with Hematoxylin and Eosin. Placental slides were read and graded as per the Amsterdam consensus paper (21) by an experienced placental pathologist (MAB), who was unaware of the clinical course and outcomes of the enrolled infants.

Inflammatory findings in the placenta included maternal inflammatory response (MIR) and fetal inflammatory response (FIR), and both were further divided into three stages per Khong et al. (21). MIR stages included stage 1: acute subchorionitis or chorionitis, stage 2: acute chorioamnionitis, and stage 3: necrotizing chorioamnionitis. FIR stages included stage 1: chorionic vasculitis or umbilical phlebitis, stage 2: involvement of umbilical vein and one or more umbilical arteries, and stage 3: necrotizing funisitis. Vasculopathy was divided into maternal vascular malperfusion and fetal vascular malperfusion. Maternal vascular malperfusion included infarcts, villous development, decidual vaculopathy, and retroplacental hemorrhage, while fetal vascular malperfusion included thrombosis, intramural fibrin, stem vessel obliteration, vascular ectasia, avascular villi, and stromal vascular karyorrhexis.

Finally, placental findings were grouped into (1) normal (N), (2) evidence of inflammation (I), (3) presence of vasculopathy (V), (4), and combined pathology of vasculopathy and inflammation (V+I).