A new, externally worn device can directly measure blood oxygen saturation in a fetus during labor and delivery. (Credit: UC Davis)

A device to directly measure blood oxygen saturation in a fetus during labor has been developed by researchers could both reduce the rate of cesarean sections and improve outcomes in difficult deliveries.

The new device is based on the same principle as the oximeter slipped on a patient’s finger at the doctor’s office. Hemoglobin in red blood cells absorbs colors of light differently depending on how much oxygen it has bound. A finger oximeter measures different wavelengths of light to calculate the oxygen saturation in blood.

Measuring blood oxygen saturation in a fetus within the mother poses additional problems. First, there is more tissue to get through to reach the fetus, so only a tiny amount of light can be reflected back to be measured noninvasively. Second, there’s the problem of separating the signal from fetal blood from that of the mother.

Experimental tests in pregnant sheep show that the new device could accurately measure oxygen levels in the fetus.

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