| 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 |
[2] Topical retinoids (caution in pregnancy): Kaplan YC, Ozsarfati J, Etwel F, Nickel C, Nulman I, Koren G. Pregnancy outcomes following first-trimester exposure to topical retinoids: a systematic review and meta-analysis. Br J Dermatol. 2015 Nov;173(5):1132-41. https://www.ncbi.nlm.nih.gov/pubmed/26215715
Topical retinoids (caution in pregnancy): Panchaud A, Csajka C, Merlob P, Schaefer C, Berlin M, De Santis M, Vial T, Ieri A, Malm H, Eleftheriou G, Stahl B, Rousso P, Winterfeld U, Rothuizen LE, Buclin T. Pregnancy outcome following exposure to topical retinoids: a multicenter prospective study. J Clin Pharmacol. 2012 Dec;52(12):1844-51. https://www.ncbi.nlm.nih.gov/pubmed/22174426
Topical retinoids (caution in pregnancy): Browne H, Mason G, Tang T. Retinoids and pregnancy: an update. The Obstetrician & Gynaecologist 2014;16:7–11. http://onlinelibrary.wiley.com/doi/10.1111/tog.12075/pdf