The human body is a complex system of genetics, and each gene plays a part in our overall health. A potential connection between variations in a specific gene, known as MTHFR, and difficulties with fertility has become a subject of growing interest. This has led to more questions about how our genetic makeup might influence the ability to conceive and maintain a healthy pregnancy.
The Role of the MTHFR Gene
The MTHFR gene contains instructions for making an enzyme called methylenetetrahydrofolate reductase. This enzyme is a component in a bodily process known as methylation, which is involved in functions including detoxification, immune response, and energy production. The primary job of the MTHFR enzyme is to convert vitamin B9, or folate, into its active form, 5-methyltetrahydrofolate (5-MTHF).
Your body requires this active form of folate for processes including the creation and repair of DNA. Some people have common genetic variations, or polymorphisms, in the MTHFR gene, with the two most studied being C677T and A1298C. While having one of these variants does not automatically signal a health problem, these genetic differences can reduce the MTHFR enzyme’s efficiency in processing folate.
The extent of this reduction depends on the specific variant. Individuals with one copy of the C677T variant (heterozygous) may have an enzyme that functions at about 65% of the normal rate, while those with two copies (homozygous) might see function drop to around 30% of normal. The A1298C variant is associated with a less significant decrease in enzyme activity. These variations are common, with estimates suggesting up to 40% of the American population may carry at least one MTHFR mutation.
Proposed Links to Infertility and Pregnancy Complications
The link between MTHFR variants and fertility is primarily theoretical, centering on how reduced enzyme function affects the body. Inefficient folate conversion can lead to lower levels of active folate and an increase in an amino acid called homocysteine. When the MTHFR enzyme is not working at full capacity, homocysteine is not effectively converted into methionine, causing its levels in the blood to rise.
Research suggests that elevated homocysteine may negatively impact both male and female fertility. In women, it has been associated with decreased egg quality and may interfere with the successful implantation of an embryo. Some studies also point to a connection between certain MTHFR mutations and a higher risk for recurrent pregnancy loss. For men, research indicates an association between MTHFR polymorphisms and a greater risk of infertility, potentially affecting sperm quality.
Beyond conception, these genetic variants have been linked to a higher incidence of certain pregnancy complications. The inefficient processing of folate is a known risk factor for neural tube defects in a developing fetus. Additionally, some studies have associated MTHFR mutations with an increased risk of preeclampsia, a condition characterized by high blood pressure during pregnancy, and potential issues with blood clotting that could affect the placenta.
Testing and Diagnosis
For those concerned about MTHFR and its potential impact on fertility, there are two primary methods of testing. A genetic test, conducted on a blood or saliva sample, identifies the specific polymorphisms a person carries, such as C677T or A1298C, and whether they have one (heterozygous) or two (homozygous) copies of the variant gene.
The second type of test is a functional one that measures the level of homocysteine in the blood. This test does not identify the gene variant itself but assesses a direct consequence of reduced MTHFR enzyme activity. Elevated homocysteine levels can indicate a problem with the methylation cycle, though other factors like deficiencies in vitamins B6 and B12 can also be a cause.
Despite the availability of these tests, many major medical organizations do not recommend routine MTHFR screening for infertility or recurrent pregnancy loss. The American College of Obstetricians and Gynecologists (ACOG) has concluded that the evidence is not strong enough to prove these gene variants are a direct cause of these issues or that testing leads to better outcomes. This is partly because the primary management strategy, folate supplementation, is often recommended to women trying to conceive anyway.
Management Approaches for Fertility
Management for individuals with MTHFR variants who are trying to conceive focuses on supporting the body’s methylation process through nutritional strategies. An important aspect is understanding the difference between types of vitamin B9. Folic acid is the synthetic form in many prenatal vitamins and fortified foods, which the body must convert into the active form.
For individuals with a less efficient MTHFR enzyme, supplementing with L-methylfolate, the already active form of folate, may be more beneficial. This form bypasses the need for conversion by the MTHFR enzyme, providing the body with the usable nutrient directly. This approach ensures an adequate supply for processes like DNA synthesis during preconception and early pregnancy.
Other nutrients also support the methylation cycle. Vitamins B6 and B12, for instance, work alongside folate and are involved in the metabolism of homocysteine. Dietary choices can also be impactful. Emphasizing foods naturally rich in folate, such as leafy green vegetables, legumes, and avocados, can help support the body’s needs. Before beginning any new supplement regimen, consult with a healthcare provider for personalized advice.