This is a prospective, observational, non-significant risk study. The study involves using non-invasive devices that measure fetal depth and tissue light scattering on the maternal abdomen. Ultrasound assessment will be performed, and five images taken at the locations indicated on Figure 1. Depth to fetus will be recorded along with measurement of all distinctive layers. All images will be captured with minimal probe pressure applied to allow accurate ascertainment of depth. Images will be anonymized, and all study data will be coded with a unique identifier. Key maternal descriptive statistics will be recorded from the medical record including BMI, height, weight (kg), parity, age and gestational age. The ISS device is a customized commercial frequency domain oximeter (Imagent, ISS Inc.; http://www.iss.com/biomedical/instruments/imagent.html) with multiple laser sources and multiple detectors. This instrument is safe, uses non-ionizing radiation. The Raydiant Oximetry Sensing System (ROSS) device is a non-invasive fetal pulse oximeter that measures fetal arterial oxygen saturation using safe, non-invasive, transabdominal near-infrared spectroscopy. The combination of these two devices makes up the Raydiant Oximetry GEN 3 device. This GEN 3 device will be positioned on the maternal abdomen of women volunteers in the late 3rd trimester. This sensor will measure light scattering and absorption for a period of about 10-20 minutes. A second measurement may be obtained for an additional site on the maternal abdomen. The Sponsor anticipates this study will require about 6-12 months to enroll all study subjects at all study sites, and another month to complete primary analyses.
The overall purpose of this study is to evaluate maternal-fetal tissue light scattering properties. The objectives of the study are: (i) integrate established mathematical principles of oxygen saturation to model with increasing accuracy the body in a body problem of fetus in mother; similar to existing pulse oximeters, the calculations will be integrated into software in the final commercial product; (ii) obtain human measurements against which both computational models and animal data can be compared.