What Is a MTHFR Mutation?

My doctor says I have a MTHFR mutation. What does that mean?
profile picture of Melissa M. Goist, MD
ByMelissa M. Goist, MD
Feb 2017
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Any medical term abbreviated with this many letters is bound to be complicated, and this one is no exception. MTHFR stands for methylenetetrahydrofolate reductase. It’s an enzyme that plays a role in producing certain amino acids (the building blocks of protein), and is especially vital for converting the amino acid homocysteine into another amino acid, called methionine.

Why is this important? In women who have this mutation, or trouble with the gene that regulates MTHFR production, too much homocysteine can build up in the blood, which can eventually lead to blood clots. These clots are dangerous at any time, but especially in pregnancy, since small clots can form between the uterus and placenta or between the placenta and the baby, leading growth restriction, low fluid levels and other potentially dangerous conditions, including miscarriage.

A MTHFR mutation is relatively rare, and even if you do test positive for the condition, you also have to produce elevated homocystine levels in order to trigger these complications. If you have a family history of blood clots or have suffered from multiple miscarriages, speak with your doctor, who can help you work out a treatment for this condition.

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