Evidence check: MTHFR in the context of Fruchtbarkeit

The role of MTHFR variants in fertility is widely discussed, but the evidence is moderate and not conclusive. MTHFR polymorphisms (e.g., C677T) can reduce folate conversion and elevate homocysteine levels. Elevated homocysteine has been associated in observational studies with recurrent pregnancy loss, preeclampsia, and neural tube defects. However, randomized controlled trials proving a causal benefit of methylfolate supplementation specifically for fertility outcomes are lacking. DNA testing alone for MTHFR is insufficient for clinical decisions; blood homocysteine and folate levels are more actionable. Many commercial claims overstate MTHFR's impact on fertility. A medical workup and targeted supplementation based on blood tests are recommended. Evidence grade: human-moderate (observational studies, no strong RCTs).