In accordance with the animal studies, reduced LIF production is observed in women with unexplained infertility and recurrent miscarriages compared to healthy fertile women in many studies (Laird et al., 1997; Hambartsoumian, 1998; Wu et al., 2013; Margioula-Siarkou et al., 2016; Margioula-Siarkou et al., 2017; Alzaidi et al., 2021), although there are exceptions (Olivennes et al., 2003; Xu et al., 2012; Karaer et al., 2014). This evidence concerns the gene LIF and Infertility.