Is MTHFR useful for fertility?

Whether MTHFR is useful for fertility requires a nuanced answer. MTHFR variants (e.g., C677T) can reduce the conversion of folic acid to active methylfolate and raise homocysteine levels. Elevated homocysteine has been associated in observational studies with increased risk of recurrent miscarriage, neural tube defects, and other pregnancy complications. However, the evidence is moderate: many carriers of MTHFR variants have normal homocysteine, and the genetic variant alone does not predict individual fertility. In clinical practice, homocysteine is usually measured before recommending methylfolate supplementation. A direct causal effect of MTHFR on fertility is not clearly established; it is one of many risk factors. Fertility is influenced by numerous genetic, hormonal, metabolic, and lifestyle factors. An MTHFR genetic test alone is not a standard tool in fertility workup. The evidence is rated human-moderate, based on observational and association studies. Caution is warranted against overblown claims from consumer genetic tests: results should always be interpreted in a clinical context.