| Study characteristics |
| Methods |
2‐arm placebo‐controlled randomised trial. |
| Participants |
52 women were randomised in a hospital setting in Germany between 1983 and 1984. The population comprised women that presented with vaginal bleeding and a closed internal cervical os. |
| Interventions |
1 vaginal suppository twice daily, containing 25 mg progesterone versus placebo. |
| Outcomes |
The study recorded the following outcomes relevant for this review: live birth, miscarriage (< 24 weeks) and preterm birth (< 37 weeks). |
| Notes |
Contact with study authors for additional information: no. Additional data from authors: no. Source(s) of funding were not reported, declarations of interest were not reported. |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Random sequence generation (selection bias) |
Unclear risk |
Sequence generation was not reported. |
| Allocation concealment (selection bias) |
Unclear risk |
Allocation concealment was not reported. |
| Blinding of participants and personnel (performance bias)
All outcomes |
Low risk |
Study participants and caregivers were blinded to treatment allocations. |
| Blinding of outcome assessment (detection bias)
All outcomes |
Low risk |
Assessors were blinded to treatment allocations. |
| Incomplete outcome data (attrition bias)
All outcomes |
High risk |
Attrition bias was > 10% balanced across study arms. |
| Selective reporting (reporting bias) |
Unclear risk |
The protocol of the study was unavailable for verification. However, this study was conducted before protocol registration became mandatory. |
| Other bias |
Unclear risk |
Source(s) of funding were not reported. |
