| Study | Reason for exclusion |
|---|---|
| Akhtar 2012 | Not RCT |
| Beigi 2016 | Comparing 2 types of progestogens |
| Berle 1977 | Combination therapy of progesterone and oestrogen was used in this study |
| Berle 1980 | Viability of the fetus was not confirmed before commencement of progesterone treatment |
| Brenner 1962 | Different population |
| Check 1995 | Combination therapy of progestogen and immunotherapy |
| Chye 2014 | Compares 2 types of progestogens |
| Corrado 2002 | Different population |
| Costantino 2016 | Participants were mixed group of women with threatened abortion and subchorionic haematoma, results of intervention cannot be obtained separately |
| Crowder 1950 | Viability was not confirmed before the commencement of the study |
| Czajkowski 2007 | The study compared 2 types of progestogen |
| El Zibdeh 2000 | Different population. Population with recurrent miscarriage rather than threatened miscarriage |
| El Zibdeh 2002 | Different population. Population with recurrent miscarriage rather than threatened miscarriage |
| El Zibdeh 2005 | Different population. Population with recurrent miscarriage rather than threatened miscarriage |
| Famina 2015 | Comparing 2 types of progestogens |
| Fuchs 1966 | Different population. Patients with recurrent miscarriage not threatened miscarriage |
| Goldzieher 1964 | Different population. Population with recurrent miscarriage rather than threatened miscarriage |
| Govaerts‐Videtzky 1965 | Viability was not confirmed before the commencement of the study |
| Hui 2015 | Comparing 2 types of progestogens |
| Johnson 1975 | Different population. Progestogen was used for the prevention of miscarriage in women with recurrent miscarriage or preterm delivery not threatened miscarriage |
| Klopper 1965 | Different population. Progestogen was used for the prevention of miscarriage in women with recurrent miscarriage not threatened miscarriage |
| Le Vine 1964 | Different population. Progestogen was used for the prevention of miscarriage in women with recurrent miscarriage not threatened miscarriage |
| Luz 1988 [pers comm] | Combination therapy of progestogen and oestrogen was used in this study |
| Moller 1965 | Viability was not confirmed before the commencement of the study |
| Nyboe 2002 | Different population. Progestogen was used for the prevention of miscarriage rather than the treatment of threatened miscarriage |
| Omar 2005 | Loss to follow‐up was more than 20% |
| Porcaro 2015 | Different population |
| Prietl 1992 | Different population. Progesterone was used for the prevention of miscarriage rather than the treatment of threatened miscarriage in IVF patients |
| Pustotina 2018 | Comparing 2 types of progestogens |
| Reijnders 1988 | Different population. Progestogen was used for the prevention not the treatment of miscarriage |
| Shearman 1963 | Different population. Progestogen was used for population with recurrent miscarriage not threatened miscarriage |
| Siew 2014 | Comparing 2 types of progestogen. |
| Siew 2015 | Comparing 2 types of progestogens |
| Smitz 1992 | Different population. Progestogen was used for the prevention of miscarriage rather than the treatment of threatened miscarriage in IVF patients |
| Sondergaard 1985 | Viability was not confirmed before the commencement of the study. |
| Song 2007 | Combination progestogen with vitamin E |
| Souka 1980 | Viability was not confirmed before the commencement of the study |
| Swyer 1953 | Different population. Progestogen was used for population with recurrent miscarriage not threatened miscarriage |
| Tognoni 1980 | Viability was not confirmed before the commencement of the study |
| Turner 1966 | Different population. The study participants do not have threatened miscarriage |
| Vincze 2006 | Comparing 2 types of progesterone |
| Zhang 2000 | Combination progesterone with vitamin E |
IVF: in vitro fertilisation; RCT: randomised controlled trial