March 2004 · Vol. 16, No. 3Fetal pulse oximetry: 8 vital questions
Will this noninvasive technique improve assessment of fetal well-being? The authors analyze what the evidence to date does and does not tell.
Dr. Vidaeff is associate professor, department of obstetrics, gynecology, and reproductive sciences, and Dr. Ramin is professor and director, division of maternal-fetal medicine, University of Texas Houston Medical School, Houston, Tex. ALEX
C .
VIDAEFF,
MD, MPH;
SUSAN
RAMIN,
MD
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KEY POINTS
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The value of this new technology might not be so much the prediction of acidosis but identification of the well-oxygenated fetus so that labor may be safely continued in the presence of a concerning—but not ominous—fetal heart rate tracing.
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The only randomized study published so far did not determine whether clinical decisions can be based solely on fetal pulse oximetry. The investigators did suggest that sensitivity and specificity for metabolic acidemia was improved in the intervention group—a promising appraisal, in contrast with previous observational data.
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When a teenage nullipara underwent labor induction for preeclampsia at 37 weeks, she was given epidural analgesia and seizure prophylaxis with magnesium sulfate. Her electronic fetal heart rate (FHR) tracing was initially reassuring, with only occasional variable decelerations, but subsequently revealed a baseline of 140 beats per minute (bpm), minimal to absent variability, no accelerations, and variable decelerations to 90 bpm with rapid return to baseline.
The tracing was interpreted as nonreassuring, and a fetal pulse oximeter was inserted. It revealed a fetal oxygen saturation rate between 45% and 50%, and labor was allowed to continue. After 3.5 hours in the second stage, the patient was delivered by outlet forceps. Her infant had Apgar scores of 8 at 1 minute and 9 at 5 minutes. The umbilical arterial pH was 7.25, and base excess
was–4.9.
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