El‐Refaie 2016

Methods	Randomised controlled study. Mansoura University Hospital and private practice settings in Mansoura, Egypt Participants were recruited from June 2012 until November 2014
Participants	225 women were recruited. Data for 116 intervention group and 108 controls Women with previous preterm birth were included (approximately 25% of each arm) Inclusion criteria: women aged 20 – 35 years old with dichorionic twin pregnancy were selected for measurement of cervical length by transvaginal sonography (TVS) at 20 – 24 weeks of gestation; cervical length of 20 – 25 mm with no symptoms or signs of impending preterm labour Exclusion criteria: known allergy or contraindication (relative or absolute) to progesterone therapy, monochorionic twins, known major fetal structural or chromosomal abnormality, single fetal demise, fetal reduction in current pregnancy, cervical cerclage in current pregnancy, medical conditions that may lead to preterm labour, rupture of membranes, vaginal bleeding
Interventions	Intervention group: received vaginal progesterone suppositories (Cyclogest®, Actavis, Barnstaple, EX32 8NS, United Kingdom) in a dose of 400 mg daily, beginning 20 ‐ 24 weeks of gestation until 37 weeks of gestation Contol/comparison group: women received standard antenatal care
Outcomes	Primary outcome: preterm labour before 34 weeks of gestation Secondary outcomes: neonatal RDS, early neonatal death (END) (not defined).
Notes	Funding sources: not reported Declarations of interest: no conflicts of interests
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer‐generated random numbers
Allocation concealment (selection bias)	Low risk	Sealed unlabeled, opaque envelopes
Blinding of participants and personnel (performance bias) All outcomes	High risk	The participants, caregivers and investigators were not blinded to group assignment
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not stated
Incomplete outcome data (attrition bias) All outcomes	High risk	9 of 125 (7%) women were lost to follow‐up in the intervention group and 17 of 125 (14%) in the control group. In addition to these 26, 42 women discontinued treatment due to noncompliance or perinatal complications. 182 women received the full course of treatment. Data for 224
Selective reporting (reporting bias)	High risk	Trial was not registered and no published protocol
Other bias	Low risk	Sample size calculation met. No baseline group differences. ITT not stated