Last Updated: June 8, 2019

Definition - What does MTHFR C677T mean?

MTHFR C677T is a mutation or polymorphism of the gene MTHFR. MTHFR is an enzyme that affects a variety of essential functions in the body. It is a gene that codes the body on how to turn an amino acid called homocysteine into methionine, a chemical compound required for DNA development and cell regeneration. MTHFR is found in every cell of the body.

It is also involved in the metabolism of folate, a vitamin necessary for the formation of the brain and spinal cord during development.

MTHFR C677T blocks the body from turning the homocysteine into methionine, blocking the development and regeneration. While research suggests there may be a link between MTHFR C677T and health disorders, including certain pregnancy conditions, there is limited research to confirm this.

FertilitySmarts explains MTHFR C677T

The presence of the MTHFR C677T mutation is correlated with high levels of homocysteine in the blood or urine. This condition is called homocysteinemia. Some suggest this condition is linked to overactive blood clotting, a condition called thrombophilia.

Certain research has considered the possibility that homocysteinemia may cause pregnancy complications, including: miscarriage, recurrent pregnancy loss, neural tube defects, preeclampsia, placental abruption, stillbirth, or fetal growth restriction. However, there is limited amount of controversial and conflicting evidence that neither proves or disproves this theory.

It has also been speculated that the MTHFR polymorphism may be associated with male infertility.

One neutral tube defect (NTD) that has been considered in relation to MTHFR C677T is anencephaly. Anencephaly causes a lack of development in a baby's brain and skull region, causing malformations and a lack of bone growth. Most babies born with anencephaly die within hours of birth. However, many babies born with the mutation do not have this condition.

The MTHFR gene mutation is hereditary, and a copy of the gene is received from each parent. Therefore it is possible to have two normal MTHFR genes, one abnormal and one normal gene (heterozygous mutation), or two abnormal genes (homozygous mutation). It is also possible to have a compound heterozygous version where there is a mutation on both MTHHFR C677T and A1298C.

Aside from MTHFR C677T, another mutation that may impact pregnancy called MTHFR A1298C also exists.

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