SMAD2 and Infertility: Specifically, several studies have suggested that SMAD2 may be a candidate gene influencing reproduction in sheep with different fecundity (Zhang, Tang, et al., 2019; Zheng et al., 2019), and the inactivation of SMAD2 in mouse can lead to endometrial dysregulation and infertility (Kriseman et al., 2019).