| 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 |
[17] Calcium: Hofmeyr GJ, Lawrie TA, Atallah AN, Duley L, Torloni MR. Calcium supplementation during pregnancy for
preventing hypertensive disorders and related problems. Cochrane Database Syst Rev. 2014 Jun
24;6:CD001059. http://www.ncbi.nlm.nih.gov/pubmed/24960615
Calcium: WHO. WHO recommendations for prevention and treatment of pre-eclampsia and eclampsia, 2011.
http://www.who.int/reproductivehealth/publications/maternal_perinatal_health/9789241548335/en/