HPL-positive infiltrating trophoblastic cells in normal and abnormal pregnancy

In a series of 24 pregnant women, placental bed biopsies were performed in the third trimester at cesarean section. All the resulting specimens contained infiltrating trophoblast with both small and giant cells, and eight also contained vascular trophoblast. On immunoperoxidase staining for HPL, some small interstitial trophoblastic cells were positive in 12 cases. Some cells of the vascular intramural trophoblast and practically all cells of the vascular intraluminal trophoblast were positive. Seven cases were normal pregnancies whereas 17 were complicated by arterial hypertension and/or fetal growth retardation. A significant correlation between abnormal pregnancy and absence of HPL-positive interstitial cells in the placental bed biopsy was found. This probably indicates a diminished overall number of HPL-positive interstitial cells in the group of abnormal pregnancies and might reflect some defect of interstitial trophoblast. Such a defect may play a role in the arrest of the physiological changes of pregnancy in spiral arteries, which has been described in pre-eclampsia and in many cases of idiopathic fetal growth retardation.