Site-dependent differences in placental stiffness in extrachorial placenta: implications for shear wave elastography...

Placental stiffness measured using shear wave elastography has been proposed as a potential indicator of placental structural characteristics. However, the measurement sites for placental stiffness have not yet been standardized. In this study, we aimed to compare the placental stiffness between extrachorial (circumvallate and circummarginate) and normal placentas to evaluate the impact of measurement site selection on the assessment.

In this cross-sectional study of 169 singleton placentas (135 normal, 34 extrachorial) delivered after 32 weeks, the shear wave velocity (SWV) was measured at the placental marginal area and near the umbilical cord insertion site. A histopathological evaluation was performed in representative cases.

The median SWV at the marginal area was significantly higher in the extrachorial placenta group than in the normal placenta group (2.20 vs. 2.07 m/s, p < 0.01). By contrast, no significant difference was observed near the umbilical cord insertion site between the groups. Secondary analyses showed consistent findings for the circumvallate and circummarginate subtypes. The histopathological examination revealed marked fibrin deposition on the fetal side at the placental margin in extrachorial placentas, which may contribute to localized increases in placental stiffness.

These findings suggest that placental stiffness measurements may be influenced by the choice of measurement site, particularly in the presence of localized structural changes such as those observed in extrachorial placentas. Measurements near the umbilical cord insertion site may be less affected by marginal structural variations and may better reflect the overall mechanical properties of the placenta.