| 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 |
[4] Effectiveness of family planning methods (% of women continuing use at 1-year): Trussell J. Contraceptive failure in the United States. Contraception. 2011 May;83(5):397-404. https://pubmed.ncbi.nlm.nih.gov/21477680/
Effectiveness of family planning methods (% of women continuing use at 1-year): National Contraception and Fertility Planning and Service Delivery Guidelines, 2019 (Draft format).