Fetal electrocardiogram (ECG) for fetal monitoring during labour

Background

Hypoxaemia during labour can alter the shape of the fetal electrocardiogram (ECG) waveform, notably the relation of the PR to RR intervals, and elevation or depression of the ST segment. Technical systems have therefore been developed to monitor the fetal ECG during labour as an adjunct to continuous electronic fetal heart rate monitoring with the aim of improving fetal outcome and minimising unnecessary obstetric interference.

Objectives

To compare the effects of analysis of fetal ECG waveforms during labour with alternative methods of fetal monitoring.

Search strategy

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (April 2009).

Selection criteria

Randomised trials comparing fetal ECG waveform analysis with alternative methods of fetal monitoring during labour.

Data collection and analysis

Trial quality assessment and data extraction were performed by the review author, without blinding.

Main results

Five trials (10,628 women) were included. In comparison to continuous electronic fetal heart rate monitoring alone, the use of adjunctive ST waveform analysis (four trials, 9671 women) was associated with fewer babies with neonatal encephalopathy (four trials, risk ratio (RR) 0.37, 95% confidence interval (CI) 0.14 to 1.00) although the absolute number of babies with encephalopathy was low (n = 19), fewer fetal scalp samples during labour (four trials, RR 0.65, 95% CI 0.59 to 0.72) and fewer operative vaginal deliveries (five trials, RR 0.89, 95% CI 0.81 to 0.98). There was no statistically significant difference in the number of babies with severe metabolic acidosis at birth (cord pH less than 7.05 and base deficit greater than 12 mmol/L) (RR 0.73, 95% confidence interval (CI) 0.49 to 1.09, data from 8907 babies), caesarean section (four trials, RR 0.93, 95% CI 0.83 to 1.03), Apgar score less than seven at five minutes (four trials, RR 0.82, 95% CI 0.58 to 1.14), or admissions to special care unit (four trials, RR 0.90, 95% CI 0.75 to 1.07). Apart from a trend towards fewer operative deliveries (one trial, RR 0.87, 95% CI 0.76 to 1.01), there was little evidence that monitoring by PR interval analysis conveyed any benefit.

Authors' conclusions

These findings provide some support for the use of fetal ST waveform analysis when a decision has been made to undertake continuous electronic fetal heart rate monitoring during labour. However, the advantages need to be considered along with the disadvantages of needing to use an internal scalp electrode, after membrane rupture, for ECG waveform recordings.

One of the included trials may not be completely reliable; this is being investigated by the relevant university and, in the meantime, the results of this review should be interpreted with great caution.