Fetal blood oxygenation level serves as a critical indicator of fetal health throughout pregnancy and labor. However, existing clinical devices predominantly employ invasive techniques, posing risks to both the fetus and the mother. To address this concern, we present a noninvasive method for precise fetal oxygenation level monitoring using time-of-flight near-Infrared Spectroscopy (ToF-NIRS). Our method is the first to achieve accurate, multichannel signal separation from two distinct layers. We conducted Monte Carlo simulations and experiments on a fiber-based ToF-NIRS prototype. Our prototype system achieves <3% estimation error in a two-layer tissue phantom. Additionally, we perform in-vivo experiments to show that our system is able to detect reduced tissue oxygenation index (TOI) levels in a human arm, through a human tissue phantom, and can perform transabdominal fetal monitoring in living sheep. Our approach is a step towards reliable and noninvasive fetal oxygenation level monitoring in clinical settings.