Graphic representing the MTHFR gene.
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What is the MTHFR gene?

Everyone has two copies of the MTHFR gene – or gene 5-methyltetrahydrofolate. All genes have important jobs in helping our bodies function, and the MTHFR gene is no different.

Common questions about the MTHFR gene: Answered

First off, what does the MTHFR gene do exactly? It’s responsible for making the enzyme, methylenetetrahydrofolate reductase (hence the MTHFR acronym and wordy gene name). This, in turn works with the B-vitamin folate to help to reduce the level of homocysteine in the body.

What does it mean to have a MTHFR gene variant?

There are two common gene variants (which is when the DNA sequence of a gene is different in different people) of this gene, and these are called C677T and A1298C. Studies have shown that women with two C677T variants have an increased risk of having children with neural tube defects (though these defects are rare, so the risk is still low). Men and women with the same two variants and elevated homocysteine levels may have an increased risk of blood clots (and people who have elevated homocysteine levels rarely have elevated levels just from the gene variants, so they should be evaluated for other risk factors that are known to cause this). Too much homocysteine in the body can be one risk factor for blood clots and heart disease, however many environmental and genetic factors influence risk for this.

Can the MTHFR gene affect pregnancy?

Associations between these common gene variants and a number of complications have been speculated and evaluated for in different ways, but no association has been found. These gene variants have not proven to be a risk factor for problems that may arise during pregnancy such as blood clots, pregnancy loss, or other negative health outcomes. Because of this, the American Congress of Obstetricians and Gynecologists (ACOG) do not recommend testing for MTHFR gene variants. If genetic testing does show a MTHFR variant, these variants on their own will not impact an individual’s medical treatment. And a medical geneticist will work hard to do a thorough and appropriate evaluation of symptoms to prevent incorrectly attributing medical problems to positive MTHFR status, which is not uncommon.

And what this all means for pregnant individuals is that prenatal care – including recommendations for prenatal vitamins or folate supplementation – will not change in major ways based on the presence of an MTHFR gene variation. Impacts include if, for example, a person has high homocysteine levels, medical providers will seek to identify all possible causes, and pregnant individuals will be advised to take standard folate dosages to reduce the risk of neural tube defects. Or, to use another example, if other symptoms indicate that it’s necessary, an individual may be referred from a medical geneticist to a hematologist or maternal–fetal medicine specialist for further evaluation.

Talk to your healthcare provider if you still have questions or concerns

If you have any questions or concerns about this, talk to your healthcare provider, as they can answer your questions.

Read more
  • Scott E. Hickey, Cynthia J. Curry, and Helga V. Toriello. “ACMG Practice Guideline: lack of evidence for MTHFR polymorphism testing. Genetics in Medicine. 15(2): 153-156. February 2013. Retrieved August 28 2018.
  • “Basic information about the MTHFR Gene.” Kaiser Permanente. The Permanente Medical Group, Inc., May 2018. Retrieved August 28 2018.
  • “MTHFR gene variant.” U.S. Department of Health & Human Services, National Institutes of Health, National Center for Advancing Translational Services. Genetic and Rare Diseases Information Center, April 18 2018. Retrieved August 28 2018.

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