The Comparison of Placental Elasticity Measured by Shear Wave Elastography and Histology.

* Kharchenko M, ** Dynnyk OB, *** Miskovic B.

* Department of Obstetrics and Gynecology, Health Center Ozalj, Ozalj, Croatia
** Department of Clinical Pathophysiology, A.A.Bogomolets  Institute of Physiology, National Academy of Science, Ukraine
*** Department of Obstetrics and Gynecology, School of Medicine, University of Zagreb, Sveti Duh Clinical Hospital, Zagreb, Croatia

Introduction. First study to investigate how placental stiffness depends on microstructural changes of placental tissue.

The aim of the study was to evaluate the association between placental histological patterns and the Young's elasticity modulus of placental tissue, obtained during ultrasound examination of placenta using the shear wave elastography mode.

Materials and Methods. Investigation included 26 placentas of full term singleton pregnancies without evident complications.  Measurement of the Young's elasticity modulus of placental tissue was carried in vitro immediately after birth, with the ultrasound machine «Ultima SE» produced by the Radmir (Ukraine) company, using the SWE mode and a 5-12 MHz linear probe. We analysed the average values ​​of Young's modulus. Thereafter, investigated placental area was fixed in formalin and sent for histological examination.  Slides were stained using hematoxylin and eosin. Van Gieson, Mc Manus and Picro-Mallori special stainings were performed as well. The following variables were analysed: the density of collagen fibers in terminal villi, the density of terminal villi, the amount of syncytial knots, intervillous fibrin deposition and perivillouse fibrin deposition.

Results. The values ​​of the Young's modulus were associated only with intervillous fibrin deposition. This association was statistically significant (p<0,001) and its correlation is shown in Table 1. The associations between elasticity modulus with the density of collagen fibers in terminal villi, the density of terminal villi, the amount of syncytial knots and perivillous fibrin deposition were not statistically significant.

 Table 1 Correlation between placental elasticity modulus and histological parameters 

	r	p
Fibrin art.	0,784	˃0,001
Collagen in TV	0,283	0,161
TV density	-0,42	0,840
Syncyt. Knots	0,186	0,364
Fibrin IVS	-0,124	0,545

^{r - spearman’s rank correlation coefficient}

Conclusions.
1. Increasing values of elasticity modulus of placental tissue associate with increasing intervillous fibrin deposition in placental terminal villi.

2. No statistically significant correlation with other histological findings can be explained by not enough samples for it and absence of placentas from pathological pregnancies. Further research is needed to determine this association.