Reduced volumetric parameters of the placenta and extravillous trophoblastic cells in complicated pregnancies may lead to intrauterine growth restriction and small for gestational age birth.

Aim: We undertook this study to determine quantitative changes of the placenta, focusing on extravillous trophoblastic cells (EVTs) in pregnancies with intrauterine growth restriction (IUGR) and small for gestational age (SGA) compared to the control group.
Methods: Placentas from pregnancies complicated with SGA-IUGR (n = 10) and control group (n = 10) were obtained after cesarean surgery and evaluated using stereological assays after routine tissue processing and Masson's trichrome staining. Mann-Whitney U-test was employed, and the level of statistical significance was set at p <0.05.
Results: Our results showed that the volumetric parameters, including the total volume and volume density of chorionic villi, intervillous spaces, blood vessels in chorionic villi, and syncytiotrophoblast, decreased significantly in the SGA-IUGR group compared to control placentas (p <0.05). Also, total volume, number of EVTs, volume, the diameter of cytoplasm, and diameter of the nucleus in these cells were significantly lower in the SGA-IUGR group (p <0.05). In addition, the nucleus to cytoplasm ratio of EVTs was also higher in the SGA-IUGR group (p <0.05).
Conclusions: There are several significant histological and stereological differences in the placenta, particularly its EVTs from the SGA-IUGR group compared to the control group. It seems that histological changes in the placental tissues could be helpful for the retrospective explanations of pregnancy complications.
(© 2022 Japan Society of Obstetrics and Gynecology.)