Assessment of placental stiffness during labor using ultrasound shear-wave elastography: a pilot study

To characterize placental elasticity during labor using shear wave elastography (SWE) in low-risk term pregnancies and to describe physiological changes across successive intrapartum stages.

In this prospective single-centre observational study, low-risk singleton pregnancies at term in spontaneous labor were examined using ultrasound SWE. Placental elasticity was assessed in vivo at multiple labor stages (early labor, active labor, and complete cervical dilatation) and ex vivo after delivery. Measurements were systematically performed in central and peripheral placental regions, both during uterine contractions and in quiescent periods, using a standardized acquisition protocol. Descriptive analyses were performed.

Thirty-nine women were included, yielding SWE measurements during early labor (n = 15), active labor (n = 25), complete dilatation (n = 29), and ex vivo (n = 24). Median in vivo placental elasticity was 10.53 kPa (SD 5.35; range 1.0-27.1). In 68% of women with repeated measurements, placental elasticity increased as labor progressed. Ex vivo elasticity values were consistently higher than intrapartum values. No significant differences were observed according to placental region, uterine contraction status, oxytocin administration, or maternal and neonatal characteristics. Histopathological examination (n = 33) revealed mainly low-grade lesions, with no evident association with elasticity values.

This study demonstrates the feasibility of placental SWE measurements during labor and provides first intrapartum references data in uncomplicated term pregnancies. The observed increase in placental stiffness during labor likely reflects physiological adaptations to labor-related hemodynamic stress.