This was a randomized controlled trial conducted in a University hospital in Malaysia, with the first participant recruited on 5 June, 2015 and the last on 10 November 2017. Our delivery unit was located within a tertiary referral facility with about 5000 deliveries per year and an overall Cesarean delivery rate of 30%. The trial was approved by the Medical Ethics Committee of University Malaya Medical Center (date of approval: 25 February 2015; reference number: 20151–971) and registered in the online searchable Malaysian National Medical Research Register (no. NMRR-15-16-23,886; https://www.nmrr.gov.my) on 6 January 2015 before trial enrolment. Malaysian research regulations governing public health institutions requires NMRR registration after a ‘preliminary’ ethics approval with ethics approval formalized after the issue of an NMRR number. In addition, the trial was also registered in the International Standard Randomised Controlled Trials Number registry, registration number ISRCTN14099170 (http://www.isrctn.com/ISRCTN14099170) on 5 Nov 2015 as Malaysian NMRR might be unrecognized. The trial was conducted in accordance with the Declaration of Helsinki on human experimentation. The study adhered to CONSORT guidelines.
Inclusion criteria were prolonged latent phase of labor (defined as an overnight hospitalization of at least 8 h for latent phase of labor), persistent contractions of at least 1 in 30 min, cervical dilation ≤3 cm and intact membranes, nulliparous (no prior pregnancy > 20 weeks), a singleton fetus, cephalic presentation, reassuring fetal heart rate tracing and ≥ 39 weeks’ gestation. Exclusion criteria included known fetal abnormalities, estimated fetal weight ≥ 4 kg or ≤ 2 kg (clinical assessment for small or large for gestational age, if either suspected then ultrasound estimation of fetal weight), contraindications to expectant management (e.g. pregnancy induced hypertension, suspected abruptio), previous uterine surgery (e.g. myomectomy or hysterotomy), known prostaglandin allergy or contraindication to vaginal delivery.
Eligible women were approached, provided with the patient information sheet, verbally counselled, and written informed consent were taken from women who agreed to participate by co-investigators LLMB and subsequently PS on investigator availability. Pre-intervention assessments were Bishop scoring by care provider, fetal heart rate tracing, and visual numerical rating scale (VNRS 0 to 10, higher score more pain) contraction pain score. Participants’ relevant demographic and clinical data were transcribed onto the Case Report Form.
Randomization and allocated intervention
Participants were randomized to induction of labor or expectant management (for at least 24 h or until indicated intervention according to care provider) by the opening of the lowest numbered sealed, numbered and opaque envelop remaining. Envelopes were prepared using a computer generated random sequence using random.org by an investigator who was not involved in the trial recruitment.
Induction of labor was undertaken according to care provider preference taking into account cervical favorability and frequency of contractions. Common methods we used were amniotomy with or without immediate titrated oxytocin infusion, titrated oxytocin infusion  or vaginal dinoprostone pessary .
In the expectant management group, spontaneous onset of active phase of labor (defined as regular contractions with cervical dilation > 4 cm) was awaited for at least 24 h; active management including labor induction might be carried based on provider and patient consensus thereafter.
A previous trial has shown Cesarean delivery rates of 23.1% vs 37.5% in the early induction group vs. the expectant management group . Applying alpha 0.05, power 80%, 1 to 1 trial arm ratio and applying the Chi Square test, 159 patients were needed in each arm.
The primary outcome was Cesarean delivery. Secondary maternal outcomes were labor duration outcomes (intervention to active phase of labor i.e. cervical dilation ≥5 cm and to delivery), epidural analgesia needed, intrapartum oxytocin, uterine hyperstimulation syndrome (non-reassuring fetal heart tracing concurrent with uterine tachysystole ≥6 contraction in 10 min), postpartum hemorrhage (blood loss ≥500 ml) and patient’s satisfaction (Likert response) to allocated intervention, during delivery and baby outcome obtained after delivery before hospital discharge. Secondary neonatal outcomes were 5-min Apgar score below 7, cord artery metabolic acidosis (pH ≤ 7 and BE [base excess] ≤ − 8 mmol/L), birth weight and admission to the neonatal intensive care unit (NICU) and admission indications.
Data were entered into a statistical software package SPSS (Version 23, IBM Corp, Armonk, NY). The Student t test was used to analyse means and continuous data and chi-square test for categorical data. Two-sided P values were reported, and a P value of < 0.05 for all variables was regarded as significant.
Women who chose not to participate received standard care and participants who decided to withdraw may do so without having to give a reason and their care was not affected. Participants were not remunerated.