PlaCEUS: Feasibility Study of Contrast-enhanced Ultrasound to Visualize Maternal Uterine Spiral Arteries Postpartum.

Overview

During pregnancy, unique blood vessels form within the uterine wall, known as spiral arteries. These vessels originate from the uterine artery, which is the main artery supplying blood to the uterus. Throughout pregnancy, spiral arteries undergo significant changes to increase blood and oxygen flow to the placenta, ensuring the developing baby receives adequate nutrients. When these arteries fail to remodel properly, complications such as pre-eclampsia or fetal growth restriction can occur. Until now, direct observation and evaluation of spiral arteries during pregnancy has not been feasible. Contrast-enhanced ultrasound may provide a breakthrough in this area. In this study, the investigators aim to use this imaging technique to visualize spiral arteries after the placenta has been delivered. If successful, this could allow to assess their structural quality. Additionally, the investigators will employ ultrasound to monitor physiological changes in the uterine artery during late pregnancy (after 37 weeks), during labour, and postpartum. By conducting these measurements, the investigators hope to develop methods for detecting spiral artery abnormalities earlier in pregnancy. Early identification could enable timely interventions and help prevent severe complications.

Adequate blood flow to the placenta is critical for normal fetal development and positive pregnancy outcomes. A key component of this process is the maternal uterine spiral arteries, which undergo significant physiological remodeling during pregnancy to meet the growing demands of the fetus. When this remodeling is impaired, it has been linked to complications such as preeclampsia, fetal growth restriction, and placental abruption. Despite its importance, directly and non-invasively assessing the maternal uterine microvasculature-particularly spiral arteries-remains difficult. Conventional Doppler ultrasound only provides indirect insights by estimating vascular resistance at a macroscopic level and cannot visualize spiral arteries or directly evaluate placental perfusion. Contrast-enhanced ultrasound (CEUS) represents a promising alternative, as it improves visualization of small vessels through the use of ultrasound contrast agents (UCAs). Since UCAs are currently not approved for use during pregnancy, this study focuses on assessing the feasibility of CEUS for visualizing persistent spiral arteries in the immediate postpartum period, as an initial step toward investigating the maternal side of the placenta. In addition, Doppler waveform analysis of the uterine arteries will be performed at three time points: before delivery, during labor, and after birth. Combining CEUS with Doppler imaging may provide a more comprehensive understanding of dynamic uteroplacental vascular changes around delivery. The primary objectives are to determine whether maternal uterine spiral arteries remain present after delivery and to evaluate the feasibility of CEUS with UCAs in visualizing and characterizing these arteries within four hours postpartum. Secondary objectives include assessing uterine artery Doppler parameters before, during, and after delivery to describe peripartum hemodynamic changes, and correlating CEUS findings at four hours postpartum with Doppler measurements.