| 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 |
[31] Benzodiazepines, oral (risk in pregnancy/breastfeeding): National Institute for Health and Clinical Excellence (NICE). Antenatal and postnatal mental health: the NICE guideline on clinical management and service guidance. Updated edition. NICE clinical guidance 192. London: NICE; 2014. Available from: https://www.nice.org.uk/guidance/cg192/evidence/full-guideline-pdf-19339686