No change in perinatal outcomes with fetal electrocardiogram
1. Deliveries using fetal electrocardiogram (ECG) did not differ from those using fetal heart-rate monitoring alone when looking at a composite of fetal or neonatal death, intubation or other markers of poor oxygen delivery.
Evidence Rating Level: 1 (Excellent)
Study Rundown: Obstetricians currently use fetal heart rate patterns as an indicator of fetal well-being during deliveries. This information can be used to make important decisions, such as whether to deliver by cesarean section. However, the heart rate patterns may be an imperfect indicator, and some are concerned that use of this type of monitoring is leading to unnecessary caesarean sections. Some European studies have suggested that the addition of fetal ECG ST-segment monitoring to heart rate monitoring can reduce the rate of caesarean sections.
This American trial did not find any difference in its primary outcome between the group using ECG plus heart rate monitoring and the group using heart rate monitoring alone. Over 11,000 deliveries were included in this study, but the trial was unable to detect a difference between the two groups. For women with uncomplicated singleton pregnancies, it seems that ECG on top of fetal heart rate monitoring does not provide additional clinical benefit.
Click to read the study in NEJM
Relevant Reading: Cardiotocography only versus cardiotocography plus ST analysis of fetal electrocardiogram for intrapartum fetal monitoring: a Swedish randomised controlled trial
In-Depth [randomized controlled trial]: This was a multicenter American randomized controlled trial involving 11,108 deliveries. Inclusion criteria were: singleton pregnancies, more than 36 weeks of gestation, attempting vaginal delivery, and cervical dilation of 2 to 7cm. Exclusion criteria included: noncephalic presentation, need for immediate delivery, and minimal fetal heart rate variability. The primary outcome was a composite of intrapartum fetal death, neonatal death, Apgar score of 3 or less at 5 minutes, neonatal seizure, umbilical-artery blood pH of 7.05 or less with a base deficit of 12 mmol/L or more, intubation at delivery, or neonatal encephalopathy. Statistical analysis revealed a difference in frequency of an Apgar score of 3 or less at 5 minutes for the open group compared to masked group (0.3% vs. 0.1%; p=0.02). This was the only difference between the two groups. No differences between the two groups were observed for overall rates of cesarean delivery (p>0.05).
Providers were specially trained to interpret fetal ECGs. However, the authors did an audit of half of the deliveries and noted that about 6% of cases with fetal ECGs were not managed according to guidelines. However, no difference was found between the two groups even when these deviations were taken into account.
Finally, the power of any negative trial must be considered. In this case, the trial was designed to have more than 85% power to detect a 40% reduction in the primary outcome in the ECG group, assuming an event rate of 1.75%. However, the actual rate of the primary outcome was only 0.72% in the control group. It is therefore possible that the trial was not adequately powered. However, given the low event rate and relatively inclusive composite primary outcome, it seems less likely that a clinically significant difference exists.
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