Method and apparatus for non-invasive fetal oximetry

A method of non-invasively determining fetal blood oxygen saturation levels, comprising:

• sending a plurality of tissue penetrating light beams from a plurality of different wavelength optical light sources through a portion of the maternal body and a portion of the fetus, and detecting the resulting transmitted or reflected light beams, thus obtaining composite maternal and fetal optical signals related to maternal and fetal arterial blood flows;
• wherein at least one light emitting device to produce said plurality of tissue penetrating light beams, and at least one light detecting device to detect said resulting transmitted or reflected light beams are located on a belt or other holder device and placed on the skin of the maternal abdomen;
• detecting the fetal heartbeat using a Doppler ultrasound device, fetal stethoscope, or other method;
• detecting pure maternal blood optical data using an optical sensor positioned to pass light beams through a portion of said maternal body that does not intersect the fetus;
• detecting the maternal heartbeat from the time varying maternal optical signals related to maternal arterial blood flow, or using maternal ECG R-wave electrodes, or other method;
• using said pure maternal blood optical data or said maternal heartbeat data to reduce the maternal portion of said composite maternal and fetal optical signals;
• using said fetal heartbeat to detect and enhance the said fetal portion of said composite maternal and fetal optical signals producing an enhanced fetal optical signal;
• and using said enhanced fetal optical signal to compute a fetal blood oxygen saturation level.

A pulse oximeter device for non-invasively determining fetal blood oxygen saturation levels, comprising:

• a plurality of optical light sources capable of producing a plurality of tissue penetrating light beams at a plurality of different wavelengths;
• at least one photodetector capable of detecting said plurality of tissue penetrating light beams after said light beams pass through tissue;
• said plurality of optical light sources and at least one photodetector positioned so as to send light beams through portions of both the maternal body and a portion of the body of a fetus, producing a set of composite maternal and fetal optical signals;
• at least one fetal heartbeat sensor producing fetal heartbeat data;
• at least one optical sensor producing pure maternal optical data, said maternal optical sensor operating on a portion of said maternal body that does not intersect the fetus;
• and/or one maternal heartbeat sensor producing maternal heartbeat data;
• at least one processor capable of taking said composite maternal and fetal optical signal data, said pure maternal optical signal data and/or said maternal heartbeat data, processing said data in the time domain and frequency domain, reducing the maternal contribution to said composite maternal and fetal optical signal data, enhancing said fetal optical signal data, and calculating a fetal blood oxygen saturation value from said amplified fetal optical signal data.