Placental Imaging Techniques

The goal of this proof-of-concept, case-control, clinical trial is to evaluate the efficacy of using two newer ultrasound technologies, quantitative ultrasound (QUS) and ultrafast power Doppler imaging (uPDI), to evaluate the health of the placenta, visualize blood flow through the placental vasculature by color Doppler imaging in singleton pregnancies with and without fetal growth restriction (FGR). * Our primary objective is to investigate the ability of using these ultrasound technologies to distinguish healthy pregnancies from those affected by FGR, a condition characterized by a fetal weight below the 10th percentile for the gestational age or abdominal circumference of the pregnancy. * Secondary aims include longitudinal evaluation of differences in QUS and uPDI imaging over gestation and changes in these measures with evolution of utero-placental insufficiency including with the development of abnormal umbilical-artery Doppler testing, diagnosis of severe FGR, identification of stillbirth, and detection of preeclampsia or preterm birth. Investigators will compare QUS/uPDI imaging and values in pregnancies determined to be healthy by approved, standard-of-care growth ultrasounds to those diagnosed with FGR. Participants will receive research ultrasounds with the experimental Verasonics Vantage 256 system (Verasonics, Inc, Kirkland, WA) utilizing uPDI/QUS every three weeks following their routine growth ultrasound evaluation until delivery. Demographic, obstetric, and delivery-related information, as well as portions of subjects' past medical history will be utilized by researchers to further contextualize imaging and variables gathered during the research ultrasounds.