What role does MTHFR play in fertility?

The role of MTHFR variants (C677T, A1298C) in fertility is often overstated. The American College of Medical Genetics (ACMG) advises against routine MTHFR testing, as evidence for a direct impact on fertility is weak. TT carriers metabolize folic acid normally, and methylfolate supplementation is not superior. Elevated homocysteine may be a risk factor for recurrent pregnancy loss, but it is effectively lowered by standard B vitamins (folic acid, B6, B12) regardless of genotype. Most studies show no significant fertility improvement from genotype-based supplementation. Direct-to-consumer tests frequently market MTHFR as a 'fertility gene,' which lacks scientific support. Clinically, factors like age, hormone status, lifestyle, and organic causes are far more relevant. Genetic testing does not replace a comprehensive fertility workup.