Modelling light propagation for fetal monitoring in utero

Abstract

About one in three births in the United States is through Cesarean section. Current monitoring techniques are insufficient to determine hypoxia and acidosis in the fetus during labor. An FDA approved transvaginal fetal pulse oximeter has been used in clinical trials to show that the device can help decrease the rate of Cesarean section. However, this technique has not been adapted into normal hospital procedure. Past pre-clinical and clinical studies have shown the feasibility of transabdominal fetal pulse oximetry. To understand the fundamentals of transabominal fetal pulse oximetry, we examined a layer model with both Monte Carlo and NIRFAST simulations. The NIRFAST model was used to model concentric spheres to understand the effect on geometry. The simulations were used in order to determine how much optical power can be detected from the fetus with a light source at 850 nm. The signal decreased as the fetal depth increased and as source-detector distance increased. The results can be used to aid in the design of a transabdominal fetal pulse oximeter.