Abstract: No studies comparing CTG monitoring during labour with an ES to intermittent auscultation were identified. Two randomised controlled trials comparing CTG monitoring during labour with an ES versus CTG without an ES were identified and included in the qualitative synthesis of results, but only one trial (n = 220) provided data for quantitative analysis. Both trials were classified as low risk of bias. There was no strong evidence that CTG with an ES has an effect on the incidence of caesarean delivery (risk ratio (RR) 0.61; 95% confidence interval (CI) 0.35 to 1.04) when compared with CTG with fetal blood sampling.There was no strong evidence supporting a reduction in the incidence of neonatal seizures (RR 0.33; 95% CI 0.01 to 8.09) or fetal acidaemia (RR 0.50; 95% CI 0.09 to 2.67) in women monitored using a CTG with an ES versus a CTG without an ES. Overall perinatal mortality could not be ascertained for this trial since data on early neonatal deaths were unavailable. Although fetal deaths were recorded, no fetal deaths occurred in either arm of the trial, and thus no risk estimates could be derived. There was no strong evidence supporting a reduction in the incidence of forceps-assisted vaginal birth (RR 0.50; 95% CI 0.05 to 5.43), hypoxic ischaemic encephalopathy (RR 0.33; 95% CI 0.01 to 8.09), admission to the neonatal intensive care unit (RR 0.40; 95% CI 0.08 to 2.02) or an Apgar less than seven at five minutes (RR 0.50; 95% CI 0.13 to 1.95). The trial did not report on artificial rupture of amniotic membranes,oxytocin augmentation of labour ormaternal satisfaction with labour. Two trials met the inclusion criteria for this review but one trial did not provide data for any of this review's outcomes. The single trial that did contribute data was underpowered to evaluate the association between CTG monitoring with an ES and the primary outcomes of interest. No recommendations for clinical practice can be made at this time. Adequately powered trials are necessary before the impact of ESs for fetal assessment in labour can be determined.

Plain-language summary: However, we did identify two randomised controlled trials looking at birth-related outcomes among women who were monitored using a CTG with an ES compared to women who were monitored using CTG without an ES. Although the review identified two eligible randomised controlled trials that were at a low risk of bias, only one trial (involving 220 women) examined the outcomes of interest in this review. Data relating to death of the baby within the first 28 days of life (early neonatal death) was unavailable but the study reported that none of the babies died before being born (fetal deaths). There was no strong evidence that CTG with an ES reduces the likelihood of caesarean delivery, forceps-assisted vaginal birth or adverse baby outcomes (such as fetal acidaemia, neonatal seizures, brain injury due to lack of oxygen (hypoxic ischaemic encephalopathy), Apgar score less than seven at five minutes or admission to the neonatal intensive care unit). These results should be interpreted with caution since the trial was underpowered as too few women were included in the trial to detect modest differences in adverse outcomes. Larger randomised controlled trials are necessary to see if CTG with an ES reduces adverse outcomes for women and their babies during the birth.