Placental morphometry in pregnancies with reversed enddiastolic flow in the umbilical artery or fetal aorta

Abstract

Fetuses with a reversed enddiastolic flow in the umbilical artery and/or aorta are at risk pregnancies and show a higher incidence of perinatal morbidity and mortality. The aim of this study was to evaluate the pathological changes in the terminal villous tree in fetuses with a reverse flow in the fetal aorta or umbilical artery. In this retrospective study, 16 cases with a reverse flow in the fetal aorta or umbilical artery (Gr. 1) were compared with gestational age matched 16 healthy pregnant women (Gr. 2). The following morphometric parameters were evaluated in 50 sections in each placenta (1600 measurements): mean vessel diameter, volume density of the villous tissue, stem villi and terminal villi. Measurements were performed using a computerized Video Image Analysis system. The mean gestational age at birth was similar in both groups (30 + 4 weeks gestation vs. 30 + 6 weeks gestation, respectively, for Gr. 1 and Gr. 2). The birth weights (985 g vs. 1780 g) and the placental weights (216 g vs. 385 g) were significantly lower in the reverse flow group. There was a significant reduction in the proportion of total villous tissue (19 % versus 45 %) and in the diameter of tissue at the terminal villi (2.1 % versus 7.6 %) in the reverse flow group. Although the mean number of vessels at the terminal villi was lower than the control group (4.1 versus 5.6), the mean and total areas of the vessels were not different. Our observations showed a significant association between the placental morphometric parameters and reversed enddiastolic flow in the umbilical artery or fetal aorta. The reduced number of functional placental units is responsible for the diminished exchange function of the placental vessels in "reverse flow" cases. This could partially explain the adverse outcome in this clinical situation.