[Significance of fetal arterial oxygen saturation (SpO2) monitoring].

The significance of fetal arterial oxygen saturation (SpO2) monitoring and its relationship with FHR patterns were studied. Continuous fetal SpO2 was obtained by infrared pulse oximetry (Nellcor N-400) in 76 cases. After amniotomy, a reflectance fetal oximetry sensor (Nellcor FS-10) was placed onto the fetal cheek. The relationship between SpO2 and FHR pattern was then studied and the following results were obtained. 1. Mean recording time was 218 min. and satisfactory records were obtained during 75% of that time. 2. Whenever the FHR was reassuring, the range of SpO2 was stable within 40-80%. 3. Variations in SpO2 values were noted during decelerative patterns. When the FHR was not reassuring, the SpO2 value tended to be lower than 40%. A more acidotic tendency was found in cases where SpO2 was below 40% prior to delivery (umbilical arterial pH 7.135 +/- 0.100 vs 7.282 +/- 0.047, p < 0.005). 4. In cases of fetal arrhythmia (congenital complete heart block 3, supra ventricular tachycardia 1), SpO2 monitoring seemed to be an effective tool for fetal surveillance during labor. Fetal SpO2 measurement seemed to be an alternative to scalp blood sampling and is especially effective in cases with a nonreassuring or uninterpretable FHR pattern such as fetal arrhythmia.