Table II.
Risk of bias in non-randomized studies of interventions of uNK level/activity in women with RM/RIF compared with healthy controls.
| Study ID | Pre-intervention |
At intervention |
Post-intervention |
Total score | ||||
|---|---|---|---|---|---|---|---|---|
| Confounding bias | Selection bias | Classification bias | Deviation bias | Missing data bias | Measurement of outcome bias | Selective reporting bias | Overall risk of bias judgement | |
| Chao et al. (1995) | Serious | Low | Low | Low | Serious | Moderate | Low | Serious |
| Lachapelle et al. (1996) | Moderate | Low | Low | Low | Serious | Moderate | Moderate | Serious |
| Lea et al. (1997) | Serious | Low | Low | Low | Low | Moderate | Low | Serious |
| Yamamoto et al. (1999) | Moderate | Low | Low | Low | Low | Moderate | Moderate | Moderate |
| Clifford et al. (1999) | Serious | Low | Low | Low | Low | Low | Moderate | Serious |
| Kwak et al. (1999) | Serious | Moderate | Low | Low | Low | Serious | Low | Serious |
| Quenby et al. (1999) | Moderate | Low | Low | Low | Low | Low | Low | Moderate |
| Quack et al. (2001) | Serious | Low | Low | Low | Low | Moderate | Low | Serious |
| Emmer et al. (2002) | Serious | Serious | Low | Low | Moderate | Low | Low | Serious |
| Michimata et al. (2002) | Moderate | Low | Low | Low | Low | Moderate | Low | Moderate |
| Lédée et al. (2004) | Serious | Low | Low | Low | Moderate | Moderate | Moderate | Serious |
| Shimada et al. (2004) | Moderate | Low | Low | Low | Low | Moderate | Low | Moderate |
| Lédée-Bataille et al. (2005) | Serious | Low | Low | Low | Low | Low | Low | Serious |
| Yan et al. (2007) | Serious | Low | Moderate | Low | Serious | Moderate | Low | Serious |
| Tuckerman et al. (2007) | Serious | Low | Low | Low | Low | Low | Low | Serious |
| Qu et al. (2008) | Serious | Low | Moderate | Low | Moderate | Moderate | Low | Serious |
| Lédées et al. (2008) | Serious | Low | Low | Low | Low | Moderate | Serious | Serious |
| Ozcimen et al. (2009) | Moderate | Low | Low | Low | Moderate | Moderate | Low | Moderate |
| Bohlmann et al. (2010) | Serious | Low | Low | Low | Low | Low | Low | Serious |
| Tuckerman et al. (2010) | Moderate | Low | Low | Low | Low | Moderate | Low | Moderate |
| Park et al. (2010) | Moderate | Low | Low | Low | Low | Moderate | Low | Moderate |
| Laird et al. (2011) | Moderate | Low | Low | Low | Low | Moderate | Low | Moderate |
| Parkin et al. (2011) | No info | Low | Low | Low | No info | Low | Low | No info |
| Bao et al. (2012) | Moderate | Low | Low | Low | Low | Moderate | Moderate | Moderate |
| Santillán et al. (2015) | Serious | Low | Low | Low | Low | Moderate | Low | Serious |
| Mariee et al. (2012) | Serious | Low | Low | Low | Critical | Low | Low | Critical |
| Giuliani et al. (2014) | Moderate | Moderate | Low | Low | Low | Low | Serious | Serious |
| Junovich et al. (2013) | Serious | Low | Low | Low | Serious | Low | Low | Serious |
| Fu et al. (2013) | Serious | Low | Low | Low | Serious | Low | Moderate | Serious |
| Wang et al. (2014) | Moderate | Low | Low | Low | Low | Moderate | Moderate | Moderate |
| Sotnikova et al. (2014) | Serious | Low | Low | Low | Low | Moderate | Moderate | Serious |
| Hosseini et al. (2014) | Moderate | Low | Low | Low | Moderate | Moderate | Moderate | Moderate |
| Liu et al. (2014) | Moderate | Low | Low | Low | Low | Low | Low | Moderate |
| Gao and Wang (2015) | Serious | Low | Moderate | Low | Low | Low | Low | Serious |
| Almasry et al. (2015) | Moderate | Low | Low | Low | Low | Moderate | Low | Moderate |
| Eskicioğlu et al. (2016) | Moderate | Low | Low | Low | Low | Moderate | Low | Moderate |
| Radović Janošević et al. (2016) | Serious | Low | Low | Low | Low | Moderate | Low | Serious |
| Chen et al. (2017) | Serious | Low | Low | Low | Low | Low | Low | Serious |
| Chen et al. (2018) | Moderate | Low | Low | Low | Low | Moderate | Low | Moderate |
| Jiang et al. (2017) | Moderate | Low | Low | Low | Low | Moderate | Low | Moderate |
| Kuon et al. (2017b) | Moderate | Low | Low | Low | Low | Moderate | Low | Moderate |
| Kuon et al. (2017a) | Serious | Low | Low | Low | Low | Moderate | Moderate | Serious |
| Fukui et al. (2017) | Moderate | Low | Moderate | Low | Moderate | Moderate | Moderate | Moderate |
| Dong et al. (2017) | Moderate | Low | Low | Low | Low | Moderate | Moderate | Moderate |
| Guo et al. (2017) | Serious | Low | Moderate | Low | Low | Moderate | Low | Serious |
| El-Azzamy et al. (2018) | Serious | Low | Low | Low | Low | Low | Moderate | Serious |
| Liu et al. (2019) | Moderate | Low | Serious | Low | Low | Moderate | Low | Serious |
| Marron and Harrity (2019) | Serious | Low | Low | Low | Low | Low | Moderate | Serious |
| Marron et al. (2019) | Serious | Low | Low | Low | Low | Moderate | Moderate | Serious |
| Li et al. (2019) | Moderate | Low | Low | Low | Serious | Low | Low | Serious |
| Huang et al. (2019) | Serious | No information | Serious | Low | Moderate | Moderate | Low | Serious |
| Toth et al. (2019) | Moderate | Low | Low | Low | Serious | Low | Low | Serious |
| Lu et al. (2020) | Serious | Low | Low | Low | Serious | Moderate | Serious | Serious |
| Wei et al., (2020) | Moderate | Low | Low | Low | Low | Moderate | Moderate | Moderate |
| Lyzikova et al. (2020) | Serious | Low | Moderate | Low | Low | Moderate | Low | Serious |
| El-Badawy et al. (2020) | Serious | Low | Low | Low | Low | Moderate | Moderate | Serious |
| Zhao et al. (2020) | Serious | Low | Low | Low | Low | Low | Low | Serious |
| Babayeva et al. (2020) | Moderate | Low | Low | Low | Low | Serious | Serious | Serious |
| Chen et al. (2021) | Moderate | Low | Low | Low | Low | Moderate | Low | Moderate |
| Liu et al. (2020) | Moderate | Moderate | Low | Low | Low | Moderate | Low | Moderate |
RIF, recurrent implantation failure; RM, recurrent miscarriage.