| Level I | Good quality evidence |
Systematic review of RCTs with consistent findings High quality individual RCT |
| Level II |
Limited quality patient orientated evidence |
Systematic review of lower quality studies or studies with inconsistent findings Low quality clinical trial Cohort studies Case-control studies |
| Level III | Other |
Consensus guidelines, extrapolations from bench research, usual practice, opinion, disease-oriented evidence (intermediate or physiologic outcomes only), or case series |
[23] Indomethacin: Reinebrant HE, Pileggi-Castro C, Romero CL, Dos Santos RA, Kumar S, Souza JP, Flenady V. Cyclo-oxygenase (COX) inhibitors for treating preterm labour. Cochrane Database Syst Rev. 2015 Jun 5;6:CD001992. http://www.ncbi.nlm.nih.gov/pubmed/26042617