F5 and Infertility: However, Casadei et al. found no significant difference in the prevalence of three thrombophilic mutations (MTHFR 677 C > T; Factor V Leiden 1691 G > A and prothrombin 20210 G > A) between 100 infertile women with unexplained infertility as compared with 200 control fertile women without a history of infertility[23].