Aboulghar 2012.

Study characteristics
Methods	Single‐centre, prospective, placebo‐controlled randomised clinical trial. The study took place in an IVF Center, Cairo, Egypt between August 2008 and March 2010
Participants	313 women at high risk of preterm birth, including 91 with twin pregnancy, with pregnancies conceived by IVF or ICSI Inclusion criteria: healthy pregnant women who conceived after IVF/ICSI between 18 to 24 weeks of gestation, with a first pregnancy, singleton or dichorionic twins, normal uterine and cervical anatomy, and normal fetal anatomy Exclusion criteria: previous pregnancy, serious fetal anomalies for which termination may be considered such as major heart anomaly or major CNS anomaly All women received progesterone injections as luteal phase support which they continued if pregnant until the day of the first ultrasound
Interventions	Intervention group: vaginal progesterone 200 mg twice daily from randomisation until delivery or 37 weeks’ gestation. Total number randomised: n = 161 women (161 analysed, 210 babies) Control group: placebo vaginal suppositories from randomisation until 37 weeks’ gestation. Total number randomised: n = 152 women (145 women analysed, 187 babies)
Outcomes	Primary outcomes: preterm birth of singleton and twin pregnancies before 37 completed weeks and before 34 completed weeks Secondary outcomes: neonatal morbidity and mortality (live‐born children who died < 28 days after delivery) and take‐home baby rate (live‐birth rate per woman). Birthweight > 2500 g; 1500 ‐ 2500 g; < 1500 g; NICU admissions
Notes	Funding sources: none reported. Declarations of interest: the authors report no financial or commercial conflicts of interest
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	States “Dark, sealed envelopes containing the intervention taken from a table of numbers” ‐ assume random as randomised study
Allocation concealment (selection bias)	Low risk	Refers to “dark, sealed, sequentially numbered envelopes” and the envelopes were picked by a nurse not involved in the study. The envelopes had been created by a third party not involved in the allocation process
Blinding of participants and personnel (performance bias) All outcomes	Low risk	States “single blinding” and that “the patient was informed about the allocated arm” so presumably the clinician/personnel were blinded
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Not clear, but probably low risk. Placebo‐controlled trial
Incomplete outcome data (attrition bias) All outcomes	Low risk	Study flow diagram clearly displays participant flow in the study 410 women recruited, 313 randomised; none lost to follow‐up in progesterone group and 6 lost to follow‐up in placebo group, and 1 excluded because of termination of pregnancy after diagnosis of trisomy 21. States “Intention‐to‐treat principle was followed during data analysis”
Selective reporting (reporting bias)	High risk	Trial registered after recruitment had started
Other bias	Low risk	Sample size calculation met. ITT analysis undertaken