Comparison of effect of CTG + STan with CTG alone on emergency Cesarean section rate: STan Australian Randomized controlled Trial (START)

Abstract

Objective: To investigate whether use of ST analysis of the fetal electrocardiogram (STan) as an adjunct to continuous cardiotocography (CTG) reduces the rate of emergency Cesarean section (EmCS) compared with CTG alone.

Methods: This was a randomized controlled trial of patients with a singleton fetus in cephalic presentation at ≥ 36 weeks' gestation, requiring continuous electronic fetal monitoring during labor at a tertiary maternity hospital in Adelaide, Australia, between January 2018 and July 2021. Participants were randomized to undergo CTG + STan or CTG alone. The calculated sample size was 1818 participants. The primary outcome was EmCS. Secondary outcomes included metabolic acidosis, a composite adverse perinatal outcome, and other maternal and neonatal morbidity and safety outcomes.

Results: The present study enrolled 970 women, of whom 967 were included in the primary analysis. EmCS occurred in 107/482 (22.2%) deliveries in the CTG + STan arm and in 107/485 (22.1%) in the CTG arm (adjusted relative risk, 1.02 (95% CI, 0.81-1.27); P = 0.89). There was no difference in the rate of adverse maternal or neonatal outcomes between arms.

Conclusions: The addition of STan as an adjunct to continuous CTG did not reduce the EmCS rate. The smaller-than-anticipated sample size meant that this study was underpowered to detect absolute differences of ≤ 5% and, therefore, this negative finding could be due to a Type-2 error. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Keywords: CTG; Cesarean section; RCT; ST analysis; STan; cardiotocography; fetal ECG; fetal electrocardiography; intrapartum fetal monitoring; randomized controlled trial.

Figure 1

Flowchart summarizing screening, enrolment, randomization and analysis in STan Australian Randomized controlled Trial (START). *One woman was randomized mistakenly before consent was obtained and, when approached, declined to participate, as did not want fetal scalp electrode (FSE). †Reasons listed in Tables S3 and S4. ‡Both women verbally requested withdrawal from study after randomization to cardiotocography (CTG) plus ST analysis (STan), as changed mind and did not want FSE. §One participant allocated to CTG received STan monitoring in addition when ST analysis started automatically after FSE was applied for clinical reasons; no STan events occurred. CEFM, continuous electronic fetal monitoring; ECG, electrocardiogram; EmCS, emergency Cesarean section.