| Table 2. Characteristics of the included studies | |||||
| Study | Study Design | Country | Period | Outcome included in the meta-analysis | FET vs Fresh aOR (95% CI) |
| Healy et al., 2010 | Retrospective cohort (population-based registry - Victoria) | Australia | 1992-2004 | Placenta previa | 0.71 (0.51, 1.00) |
| Ishihara et al., 2014 | Retrospective cohort (nationwide registry) | Japan | 2008-2010 | Pregnancy induced hypertension Placenta previa Placenta accreta | 1.58 (1.35, 1.86) 0.91 (0.70, 1.19) 3.16 (1.71, 6.23) |
| Kaser et al., 2015 | Case-control study (single-center analysis) | United States | 2005-2011 | Placenta accreta | 4.54 (1.65, 12.47) |
| Opdahl et al., 2015 | Retrospective cohort (nationwide registry) | Denmark, Norway and Sweden | 1988-2007 (Sweden and Norway) 1997-2007 (Denmark) | Pregnancy induced hypertension | 2.39 (1.48, 3.86) |
| Rombauts et al.,2014 | Retrospective cohort (single-center analysis) | Australia | 2006-2012 | Placenta previa | 1.13 (0.61, 2.10) |
| Sazonova et al., 2012 | Retrospective cohort (nationwide registry) | Sweden | 2002-2006 | Pre-eclampsia Placenta previa | 1.32 (1.07, 1.63) 0.32 (0.19, 0.54) |