Digital foetal scalp stimulation versus foetal blood sampling to assess foetal well-being in labour: a multicentre randomised controlled trial

Objective: To establish whether digital foetal scalp stimulation (dFSS) performs better than foetal blood sampling (FBS) in terms of reducing the rate of caesarean section (CS) in labour, without adversely affecting perinatal outcomes.

Design: A multicentre parallel-group randomised controlled trial.

Setting: Maternity centres in Ireland.

Population: The study aimed to randomise 2500 nulliparous women who required a second-line test of foetal well-being in labour due to abnormal cardiotocography (CTG).

Methods: Participants were randomly allocated to dFSS or FBS in a 1:1 ratio. Analysis was according to the published protocol and included a meta-analysis of the pilot study data and trial data.

Main outcome measures: The primary outcome was CS.

Results: Due to lower-than-expected randomisations, the trial concluded early. Of 534 consented participants, 124 had a second-line test of foetal well-being in labour and 43 (34.7%) were randomised; 20 to dFSS and 23 to FBS. The rate of CS was 40.0% (8/20) in the dFSS group and 47.8% (11/23) in the FBS group (absolute difference 7.8%; OR 0.73, 95% CI 0.22-2.44). The rate of CS was lower in the dFSS group when the trial data were included in a meta-analysis with the pilot data (n = 50), although the confidence limits were wide (OR 0.41, 95% CI 0.17-0.96). There was no significant difference in rates of adverse perinatal and maternal outcomes. Of the nonrandomised participants who received a second-line test, 65% (53/81) received dFSS.

Conclusions: The small sample size limits the ability to conclude whether dFSS performs better as a second-line test of foetal well-being in labour than FBS. A clinician preference for dFSS was apparent, even though robust evidence is lacking.

Trial registration: This trial was prospectively registered on ClinicalTrials.gov on the 31st of March 2022.

Clinicaltrials: gov Identifier: NCT05306756 (Access at https://clinicaltrials.gov/study/NCT05306756?cond=fetal blood sampling&rank=3).