Antepartum, transabdominal near infrared spectroscopy: Feasibility of measuring photon migration through the fetal head in utero

Objective: We report the feasibility of measuring photon migration through the fetal head in utero using antepartum, transabdominal, near infrared (NIR) spectroscopy. Methods: We developed a continuous wave (CW) spectrometer that incorporates a halogen light source, silicon photodetectors, and a differential processing circuit for antepartum, transabdominal, NIR spectroscopy. By placement of the light source and photodetector on the midline of the maternal abdomen above the fetal head at a separation (∼10 cm) large enough for the light to propagate through maternal and fetal tissues via multiple scattering events before being detected at the surface and the use of filtered illumination and detection at wavelengths (760 nm, 850 nm), which coincide with the absorption bands of oxygenated and deoxygenated hemoglobin in the NIR window, we performed studies to evaluate whether antepartum, transabdominal NIR spectroscopy can measure photon migration through the fetal head in utero. Results: The results demonstrate that the CW spectrometer we developed can be employed to make NIR measurements from the maternal abdomen at a 10 cm source-detector separation, with an excellent signal-to-noise ratio. Furthermore, a variety of antepartum, transabdominal NIR measurements that we performed on patients undergoing a routine nonstress test demonstrate the feasibility of measuring photon migration through the fetal head in utero. Conclusions: Preliminary assessment of transabdominal NIR spectroscopy suggests that this technique can enable photon migration through the fetal head in utero. This is an important step towards the development of this technique for measuring and quantifying fetal cerebral blood oxygenation in utero.