Laser Doppler Flowmetry and Fetal Oxygenation

Due to the inaccessibility of the fetus, continuous direct monitoring of the carotid arterial blood pH and gas values is not yet feasible. Information on the fetal arterial pH and blood gas values can be obtained from the capillary circulation of the presenting part, usually the fetal scalp. As long as the scalp blood flow remains undisturbed, the peripheral blood pH and gas values will form a reasonable reflection of the carotid arterial values. However, if scalp blood flow decreases, the difference between the carotid arterial and peripheral blood pH and gas values will increase, due to local skin metabolism rendering these values questionable for fetal monitoring.