The influence of paternal MTHFR C677T polymorphism on in vitro fertilization outcomes in male Han population

The methylenetetrahydrofolate reductase (MTHFR) regulates the metabolism of homocysteine in the human body, and MTHFR C677T polymorphism is correlated with male infertility among Asian populations. The relationship between paternal MTHFR C677T polymorphism and clinical outcomes is unclear due to conflicting study findings. In the current retrospective study, we enrolled 849 infertile couples from the First Affiliated Hospital of USTC, categorizing them into three subgroups based on their paternal MTHFR 677 genotype: CC, CT and TT. The clinical pregnancy (CC: 60.8%, CT: 62.5%, TT: 63.7%; p = 0.83), implantation (CC: 36.6%, CT: 42.2%, TT: 40.5%; p = 0.15), blastocyst formation (CC: 49%, CT: 48.4%, TT: 50.6%; p = 0.49), good-quality embryo (CC: 48.3%, CT: 49.8%, TT: 51.3%; p = 0.19), and normal fertilization (embryo development) (CC: 67.1%, CT: 66.2%, TT: 67.5%; p = 0.51) rates were comparable among all groups. Similarly, the live birth (CC: 54.2%, CT: 53.2%, TT: 53.7%; p = 0.97) and miscarriage (CC: 10.9%, CT: 14.9%, TT: 15.7%; p = 0.45) rates were comparable among the three cohorts. Regarding neonatal outcomes, the Apgar score, gestational age at delivery, neonatal sex, birth weight, birth height and preterm birth rates were non-significant among all groups. Finally, the rates of birth defects were also comparable among individuals of all groups (CC: 0%, CT: 0.3%, TT: 1.9%; p = 0.18). These findings suggest that paternal MTHFR C677T polymorphism does not exert any discernible effect on embryo quality, neonatal outcomes or birth defects in vitro fertilization (IVF) treatment. Therefore, in our population, paternal MTHFR C677T polymorphism is not informative in explaining IVF failure. Further studies, however examining the other enzymes in the folic acid pathway are warranted.