Prenatal Vitamins and MTHFR

Most prenatals are multivitamins that contain key nutrients known to support fetal development and maternal health. These include folate, B‑vitamins, iron, iodine, vitamin D, calcium, and usually also Vitamin A (as beta-carotene), vitamin C, zinc. Some higher-end products may also contain docosahexaenoic acid (DHA), choline, and various trace minerals.

Most important ingredients: 

• Folate/folic acid (or methylfolate): usually around 400-800 mcg to support healthy fetal development and reduce risk of neural tube defects. RDI during pregnancy is 600 mcg.
• Iron: to support red blood cell formation and reduce risk of anemia.
• Iodine: to support maternal thyroid function and fetal brain development.
• Vitamin D: for calcium absorption and bone health.
• Calcium: to support bone health
• B‑complex: B1, B2, B3, B5, B6, B7 (biotin), B12 to support energy production, red blood cell formation, and nervous system health.
• Vitamin C: to support iron absorption, antioxidant capacity, collagen formation, immune health. 
• Vitamin A: limited amounts, usually as beta‑carotene, to support antioxidant capacity and eye development. 
• Vitamin E: as an antioxidant.
  
  

Additional ingredients 

• Zinc: to support immune function and growth.
• Magnesium: for muscle health and nerve function.
• Copper, selenium, manganese: in trace amounts as part of a standard multivitamin‑mineral profile.
• DHA (omega‑3): for fetal brain and eye development
• Choline: for healthy neurodevelopment

It is estimated that pregnancy may increase folate requirements by as much as five‑ to ten‑fold.¹ This is because folate is required for many aspects of fetal development, including nucleic acid synthesis, red blood cell formation, and closure of the neural tube.

How pregnancy changes folate levels

Pregnancy substantially increases folate need because of:

• Rapid growth of the maternal tissues, placenta, and fetus. These tissues have high rates of DNA synthesis and cell division.²
• The mother’s folate is transferred to the fetus, which significantly reduces maternal stores.
• Plasma volume expansion due to growth of the uterus can dilute circulating folate concentrations.
  
  

Daily folate supplementation can help keep serum folate in or above the mid‑normal range. However, if folate intake is inadequate or the body is not properly metabolizing ingested folate, levels can decrease. This can lead to an increase in homocysteine as well as megaloblastic changes to red blood cells and anemia.³

The World Health Organization states that a threshold of >906 nmol/L (400 ng/mL) is the optimal folate concentration for NTD prevention in women of reproductive age, including during early pregnancy.⁴

The MTHFR genetic mutation can cause reduced function of the MTHFR enzyme, which is involved in metabolizing folate. As a result, folate levels may decrease. 

Supplementing with methylfolate (the biologically active form of folate) is often a more efficient way to support healthy folate levels in women with MTHFR. 

High intake of folic acid, on the other hand, can lead to excess levels of unmetabolized folic acid (UMFA) in the blood, which may increase risks during pregnancy, including gestational diabetes and neurodevelopmental impacts on the fetus.⁵

However, standard guidelines still recommend folic acid, even for those with MTHFR.

A prenatal designed for those with MTHFR will typically contain 5‑methyltetrahydrofolate (5‑MTHF/L‑methylfolate) as the primary folate source, rather than folic acid. This dose will be provided in the active folate range. Some studies have shown that methylfolate increases blood folate and erythrocyte folate effectively in women with MTHFR variants, and is not limited by reduced MTHFR enzyme activity.⁶

Active forms of B vitamins - including methylcobalamin (instead of cyanocobalamin) and pyridoxal‑5‑phosphate/P5P (instead of pyridoxine) participate directly in one‑carbon metabolism and methylation processes. Although these forms of nutrients generally cost more than synthetic forms, they are more efficient for those affected by impaired methylation.

A quality prenatal should provide key nutrients such as iron, iodine, vitamin D in their active forms where possible. Active nutrients are already in the specific chemical form that the body can use immediately, which means they can bypass the conversion processes required for inactive or synthetic nutrients.

MTHFR variants can pose a risk to a healthy pregnancy when folate levels are low and homocysteine becomes elevated. 

Women with MTHFR who are pregnant or planning a pregnancy should be aware of the following:

• The form of folate
  MTHFR variants reduce the body’s ability to generate methylfolate, so maintaining sufficient folate intake is essential for healthy fetal development and to maintain normal levels of homocysteine.
  Although many clinicians still recommend standard folic acid (400 mcg/day) even for women with MTHFR, methylfolate is generally considered a superior option. Methylfolate is immediately usable in the body and requires no further conversion.
  
  
• Homocysteine levels
  People with MTHFR variants are at higher risk of elevated homocysteine, especially if they are low in folate, B12, or B6. High homocysteine is especially serious during pregnancy as it can cause vascular inflammation, potentially leading to complications such as preeclampsia, placental rupture, gestational diabetes, and early pregnancy loss. Monitoring homocysteine levels should be a priority for all women during pregnancy. Supplementing with methylfolate, B12, and B6 is recommended.
  
  
• Potential risks of folic acid
  Folic acid is readily available from both over-the-counter (OTC) preparations and prescription medications, and is also present in many fortified foods.
  Women of childbearing age often exceed the recommended daily intake of folic acid due to mandatory fortification combined with supplemental use. This can be serious for women with MTHFR due to their inability to process folic acid efficiently, potentially leading to unmetabolized folic acid accumulation. Avoiding fortified foods and folic acid supplements may be advisable.
  
  
• Health history
  Women with a personal or family history of pregnancy loss and/or cardiovascular issues should consult their health professional regarding their maternal health. A personalized supplementation and nutrition plan that accounts for health history and genetic makeup is essential for supporting pregnancy health. 

Many ‘normal’ prenatals contain folic acid, the synthetic (and inactive) form of folate. Research has suggested that high intake of folic acid may pose serious health risks for women with the MTHFR variant as they have a reduced ability to process folic acid. This leads to an accumulation of unmetabolized folic acid (UMFA), which has been associated with adverse pregnancy outcomes as well as vitamin B12 deficiency.⁹

Taking a prenatal that contains methylfolate can avoid these risks by bypassing the MTHFR conversion step.

The benefits of healthy folate levels during pregnancy include:¹⁰

• Reduced risk of neural tube defects in the baby.
• Reduced risk of other structural malformations, including certain congenital heart defects and orofacial clefts.
• Lower risk of preterm birth, low birth weight, and fetal growth restriction.
• Support for normal brain development through roles in DNA synthesis and proper cell proliferation in brain tissue.
• Maintaining production of S‑adenosylmethionine, which is required for methylation processes contributing to brain development, structure, and function, as well the synthesis of neurotransmitters (including serotonin and catecholamines).
• Conversion of homocysteine to methionine, which reduces risk of homocysteine accumulation and its association with pregnancy complications.  
• Prevention of maternal megaloblastic anemia
• Support for healthy red blood cell formation, delivery of oxygen to the tissues, and fetal growth.

Recommended daily intake of folic acid during pregnancy is 600-800 mcg. People planning a pregnancy are advised to start taking folic acid at least one month before they start trying.¹¹

Most prenatal vitamins contain 0.8 mg or 800 mcg of folic acid.

The upper limit established for folic acid from dietary supplements and fortified foods is 1000 mcg for pregnant and lactating women.  

Research regarding methylfolate dosage during is still currently limited, so recommendations are generally the same for folic acid: around 600 µg/day in pregnancy, and 400 µg/day in  women of reproductive age.

However, one study reported that supplementation of pregnant women with 400 mcg/day (6S)-5-methyltetrahydrofolic acid (from Quatrefolic) until the 24th week of pregnancy was more efficient in increasing methylfolate blood levels than the same dose of folic acid.¹²

Dietary folate is the natural form of vitamin B9 present in foods such as leafy greens, legumes, and citrus fruits.

Bioavailability of naturally occurring folates can vary significantly, as it depends on how the folates are released from the food and absorbed in the intestine. Other foods, medications, and health conditions can also affect the digestive process, which means that dietary folates are typically not a reliable source of folate.

Folic acid is the synthetic form of folate commonly used in dietary supplements (including prenatals) and fortified foods. It is cheap, highly stable, and has been shown in numerous clinical studies to prevent NTDs.¹³

Folic acid must be converted to its active form in the body before it can be used. People with MTHFR variants have limited function of this enzyme, so folic acid may be less beneficial. In addition, folic acid can mask vitamin B12 deficiency, which can have serious health concerns for both mother and baby.

Methylfolate is an active form of folate and the predominant form in the human body. It does not require conversion to be used by the body, so it is ideal for women with MTHFR genetic variants that limit the ability to process synthetic folic acid. Methylfolate also does not mask Vitamin B12 deficiency, and does not cause accumulation of unmetabolized folic acid (UMFA) in the blood.

While both folic acid and methylfolate are shown to be effective at increasing folate levels, methylfolate is suggested as a superior alternative for women with MTHFR during pregnancy.¹⁴