Fetal Pulse Oximetry

Fetal Pulse Oximetry

Bakr AF, Al-Abd M, and Karkour T. Fetal Pulse Oximetry and Neonatal Outcome: A Study in a Developing Country. J Perinatol (November 2005) 25: 759-62. [Full Text]

Background. The aim of this cohort, prospective study was to compare the diagnostic value of intrapartum fetal pulse oximetry (FPO) with that of fetal scalp blood gas (FSBG) for an abnormal neonatal outcome in cases with abnormal fetal heart rate (FHR) tracings.

Methods. Fetal oxygen saturation was continuously monitored with Nellcor N-400 FPO during labor. Simultaneous FSBG determinations were obtained. The results were analyzed in relation to umbilical arterial cord blood pH and neonatal outcome. Studied FPO cutoff levels were 30 and 40% hemoglobin saturation and that of FSBG pH was 7.2.

Results. During the study, there were 9825 deliveries; 415 had abnormal FHR. Only 150 fulfilled the whole screening panel. When the outcome variable was umbilical arterial pH, the positive predictive values of the three methods (FPO30, FPO40, FSBG) were 57, 61 and 65% and the negative predictive values were 43, 39 and 35% respectively. The sensitivity of FPO30 was highest (75%). Considering abnormal neonatal outcome, again the sensitivity was also highest for FPO30 (89%). The sensitivity of FSBG was 82%. The specificity of the three methods were 53, 49 and 38% respectively.

Conclusion. The diagnostic value of intrapartum FPO compares favorably with FSBG. FPO seems to be a reliable and less invasive tool and may decrease unnecessary interventions and unnecessary fetal scalp blood sampling in cases of suspected fetal distress. The FPO cutoff of 30% saturation defined by previous studies appears to be appropriate.

Comments: The major drawback to using fetal pulse oximetry as an aid to decision making regarding abnormal FHR tracings is the time factor. The fetal pulse oximetry results in this study were the average oxygen saturation from a 30-minute tracing. In the setting of possible fetal distress, 30 minutes seems like a prohibitively long time to wait for a test result. In most cases, I think our obstetricians would push ahead with a caesarean delivery rather than chance that the baby have a worse outcome due to the delay caused by this testing. ABK

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