A Cochrane review [Abstract] 1 included 7 studies comparing fetal pulse oximetry (FPO) and cardiotocography (CTG) with CTG alone, with a total of 7 834 pregnancies. Differing entry criteria necessitated separate analyses, rather than meta-analysis of all trials. Four trials from 34 weeks not requiring fetal blood sampling prior to study entry reported no significant differences in the overall caesarean section rate between those monitored with FPO and those not monitored with FPO or for whom the FPO results were masked (RR 0.99, 95% CI 0.86 to 1.13, n = 4008). In one small study, there was evidence of a higher risk of caesarean section in the group with fetal oximetry plus CTG than in the group with fetal ECG plus CTG (RR 1.56, 95% CI 1.06 to 2.29; n = 180). Neonatal seizures and hypoxic ischemic encephalopathy were rare. No studies reported details of assessment of long-term disability.
There was a statistically significant decrease in caesarean section for nonreassuring fetal status in the FPO plus CTG group compared to the CTG group, gestation from 34 weeks (average RR (random-effects) 0.65, 95% CI 0.46 to 0.90, n = 4008, I² = 63%) There was no statistically significant difference in caesarean section for dystocia when FPO was added to CTG monitoring, compared with CTG monitoring alone, although the incidence rates varied between the trials.
A review 2 re-evaluated the use of FPO and 7 RCTs of FPO.The largest trial with 5341 entries failed to show any reduction. The negative result was explained by the use of a different cutoff value for fetal oxygen saturation compared to the other RCT; in addition, there were differences in the indications for cesarean section due to dystocia and in the definition of non-reassuring fetal status. An abnormal FPO value, defined as the fetal oxygen saturation value <30% for at least 10 min, was useful for making a diagnosis of fetal acidosis.
Comment: The quality of evidence is downgraded by inconsistency (variability in results across studies).
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