Methylenetetrahydrofolate reductase (MTHFR) is the name of a gene that produces an enzyme, also called methylenetetrahydrofolate reductase. If a person carries the genetic mutation that inhibits production of this enzyme, it can result in hyperhomocytenemia, which is an elevated level of an enzyme called homocysteine found in blood plasma.

When the body is deficient in methylenetetrahydrofolate reductase, its ability to absorb folate (also known as vitamin B9), such as folic acid, is inhibited. Folic acid and B9 are both essential to the development and health of the fetus.

MTHFR and Pregnancy

Because of a mother with MTHFR’s inability to efficiently metabolize folic acid and vitamin B9, the disorder has been linked to a variety of pregnancy complications such as chromosomal abnormalities, such as Down syndrome, and congenital malformations.

Elevated levels of homocysteine have been associated with placental disease, preeclampsia and recurrent pregnancy loss. 21% of women with high levels of homocysteine experience recurrent pregnancy loss.


Because MTHFR is a blood-based disease with many varieties, symptoms vary depending on the exact mutation of the disease. They can include:

  • blood clots
  • depression
  • anxiety


Blood testing is the most accurate way to screen for MTHFR. This is especially true if women have a history of complicated pregnancies, including recurrent pregnancy loss and/or stillbirths, or if they have given birth to a child with neural tube defects, such as spina bifida.