Problem 1: What potential confounders were considered? How were confounders measured?
Problem 2: What methods were used to address confounding? In study design? In analysis? What are the number of participants at each stage of study, eligible, included in study, completed follow up, analyzed? What are the reasons for non-participation?
Reference:
Erenel H, Aydogan Mathyk B, Sal V, Ayhan I, Karatas S, Koc Bebek A. Clinical characteristics and pregnancy outcomes of Syrian refugees: a case-control study in a tertiary care hospital in Istanbul, Turkey. Arch Gynecol Obstet. 2017 Jan;295(1):45-50