| 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 |
[22] Ondansetron, parenteral (in pregnancy): Kaplan YC, Richardson JL, Keskin-Arslan E, Erol-Coskun H, Kennedy D. Use of ondansetron during pregnancy and the risk of major congenital malformations: A systematic review and meta-analysis. Reprod Toxicol. 2019;86:1‐13. https://pubmed.ncbi.nlm.nih.gov/30849498/
Ondansetron, parenteral (in pregnancy): Huybrechts KF, Hernández-Díaz S, Straub L, et al. Association of Maternal First-Trimester Ondansetron Use With Cardiac Malformations and Oral Clefts in Offspring. JAMA. 2018;320(23):2429‐2437. https://pubmed.ncbi.nlm.nih.gov/30561479/
Ondansetron, parenteral (in pregnancy): Huybrechts KF, Hernandez-Diaz S, Straub L, et al. Intravenous Ondansetron in Pregnancy and Risk of Congenital Malformations [published online ahead of print, 2019 Nov 15]. JAMA. 2019;323(4):372‐374. https://pubmed.ncbi.nlm.nih.gov/31730152/