Morphological characteristics of placentas associated with idiopathic intrauterine growth retardation: a clinicopathologic study

Abstract 

Objectives

To investigate histopathologic findings, placental diameters and characteristics of syncytial knots in the placentas from idiopathic intrauterine growth retardation (IUGR) pregnancies, and to compare them with a normal birth weight group.

Study design

Based on strict eligibility criteria, this prospective case–control study included 52 term placentas from idiopathic IUGR pregnancies and 69 term placentas from normal birth weight pregnancies. The study was carried out at the Clinical Hospital Centre, Split, where all placentas were collected and examined. For each placenta, diameters were measured and the following histopathologic findings were recorded: infarction, intervillous thrombosis, abruption, villous branching and maturation, chorioamnionitis, decidual vasculopathy and hemorrhagic endovasculitis for each placenta. In addition we assessed quantitative (number of syncytial knots and number of syncytial nuclei per syncytial knot) and qualitative (density and surface area) characteristics of syncytial knots in each placental sample. Statistical significance was tested using χ²-test, Student's t-test and Mann–Whitney U-test. Statistical significance was set at P≤0.05.

Results

There was no difference in investigated histopathologic findings between idiopathic IUGR placentas and control group placentas. Placental diameters correlated significantly with neonatal birth weight (r=0.64; P<0.01); with higher birth weight there is an increase in placental diameters. Syncytial knots from idiopathic IUGR had significantly smaller surface area (Z=2.637; P=0.008) and higher density (Z=3.225; P=0.001) compared with the control group, while there is no difference in number of syncytial knots per individual villus, total number of syncytial knots in each placenta sample or number of syncytial nuclei per syncytial knot.

Conclusions

The investigated histopathologic findings in idiopathic IUGR placentas are incidental, with no higher frequency than in placentas from uncomplicated pregnancies, and should not be considered as possible causative factors for idiopathic IUGR. The demonstrated qualitative changes of syncytial knots in placentas associated with IUGR could represent a compensatory mechanism.

Keywords: Idiopathic intrauterine growth retardation, Histopathologic findings, Placenta, Syncytial knots