Emerging ultrasound-based imaging of the placenta during complications of pregnancy

The placenta is an essential organ that develops throughout pregnancy, facilitating the exchange of nutrients, waste products, hormones, and antibodies between the fetal and maternal circulations. Insufficient development of placental structure and function is associated with various pregnancy disorders, including preeclampsia (PE), fetal growth restriction (FGR), gestational diabetes mellitus, preterm birth, and potential fetal cardiovascular diseases. Analyzing the spectrum of placental pathology in both normal and abnormal placentas helps to better understand disease pathologies and reduce maternal and fetal morbidity and mortality. Acoustic imaging techniques have been demonstrated as promising noninvasive methods for efficiently evaluating placental impairment. Ultrasound imaging (US) and Doppler ultrasound are standard modalities for assessing placental anatomy and gross morphology, due to their accessibility, affordability, and lack of ionizing radiation exposure. Preclinical studies provide opportunities to develop new acoustic-based imaging technologies. For example, using conventional US data, quantitative ultrasound (QUS) has been used to evaluate microstructural changes in placental tissue noninvasively. Shear-wave elastography (SWE) can provide diagnostic information about placental elasticity, reflecting tissue stiffness and biomechanical properties. Photoacoustic Imaging (PAI) provides valuable insights into placental hypoxia and inadequate vascular remodeling. Contrast-enhanced ultrasound (CEUS) and contrast-enhanced photoacoustic imaging (CEPA) can enable quantification of molecular expression changes in the placenta. In this article, we review major placental-related diseases and their potential consequences, as well as preclinical acoustic imaging modalities that hold potential for improving the assessment of placental health during pregnancy.