By Madeline Sheppard, Naturopath, Living Holistic Health — a practical guide to MTHFR in pregnancy, from folate forms to testing.
If you’ve read our article on prenatal supplements and what the evidence really shows, you’ll know that folate is one of the most important nutrients in pregnancy planning and care. It’s also one of the most misunderstood. This article is the first in a series expanding on that topic. It’s dedicated entirely to one question I’m asked almost every week in clinic: “What does it mean if I have MTHFR?”
MTHFR support in pregnancy has become a popular search term, and for good reason. Genetic testing is more accessible than ever. More of my patients are arriving with a raw data file or a pathology report showing an MTHFR variant. They’re often unsure what it means for their pregnancy or their baby. This article walks through what MTHFR actually is and why unmetabolised folic acid matters. It also covers how to choose the right form of folate. It also looks at why methylation support in pregnancy is about so much more than one gene.
What Is MTHFR, and Why Does It Matter in Pregnancy?
MTHFR stands for methylenetetrahydrofolate reductase — an enzyme, and the gene that codes for it. This enzyme converts dietary folate into 5-methyltetrahydrofolate (5-MTHF), the active form your body actually uses. 5-MTHF is essential for two connected jobs. It supports healthy neural tube development in your baby. It also recycles homocysteine, an amino acid that needs to stay within a healthy range throughout pregnancy.
Common variants in the MTHFR gene can reduce how efficiently this enzyme works. The two we test for most often are C677T and A1298C. According to PubMed, a 2026 review in Frontiers in Nutrition describes MTHFR genetics and vitamin B12 status as critical modifiers of folate metabolism in pregnancy (Yang & Li, 2026). These modifiers directly influence outcomes for both mother and baby. Having an MTHFR variant doesn’t mean something is wrong with you. It means your body may need a different approach to folate than the general population — exactly the kind of thing we assess for in a naturopathic pregnancy consultation.
Key Risk Factors for MTHFR SNPs
MTHFR variants are common. Heterozygous C677T or A1298C changes show up in a large proportion of the population. Having one copy of a variant is generally a much smaller consideration than having two. A few things raise my index of suspicion and prompt a closer look:
A personal or family history of recurrent pregnancy loss is one of the strongest signals. According to PubMed, a 2026 study of women experiencing recurrent pregnancy loss found MTHFR C677T carried heterozygously in 57.8% of participants and A1298C in 53.1% (study, 2026). Homozygous carriers of either variant were significantly more likely to have experienced multiple losses. A separate 2026 study looked at Georgian women with unexplained recurrent pregnancy loss. It found the homozygous 677TT genotype significantly more prevalent than in fertile controls, and just over half of MTHFR 677CT/TT carriers had elevated homocysteine (study, 2026).
A few other factors raise the likelihood of a clinically relevant MTHFR picture. These include a personal or family history of neural tube defects in a previous pregnancy, a history of elevated homocysteine on pathology, and unexplained recurrent miscarriage. A family history of early cardiovascular disease is worth noting too, since homocysteine and cardiovascular risk share the same recycling pathway. A 2025 study compared women with recurrent spontaneous abortion to fertile controls. It found both MTHFR C677T (TT genotype) and MTRR A66G variants more common in the pregnancy loss group, with the MTHFR TT genotype linked to lower red blood cell folate (study, 2025).
I don’t raise any of this to alarm you. I raise it so you can see why, if any of these apply to you, targeted testing and a personalised folate strategy deserve priority well before or early in pregnancy.
Unmetabolised Folic Acid: Why Folate Form Matters with MTHFR in Pregnancy
This is one of the most important — and least discussed — parts of the folate conversation. Most prenatal multivitamins, and almost all fortified foods, use synthetic folic acid. Folic acid needs to pass through several conversion steps, via the MTHFR enzyme, before your body can use it. If you’re taking in more folic acid than your body can convert, the excess can circulate in your blood as unmetabolised folic acid (UMFA). This happens more easily if you carry a reduced-function MTHFR variant.
UMFA isn’t just an inactive bystander. Researchers are increasingly looking at what circulating UMFA means for pregnancy physiology, including at the level of the placenta. This is precisely why assessing which form of folate you’re taking matters as much as whether you’re taking one at all.
What the Research Shows About Folate Form
The encouraging news is that this is a solvable problem. According to PubMed, a 2026 randomised controlled trial compared 5-MTHF against folic acid in a prenatal multivitamin over 24 weeks. The active-folate group had far fewer participants with any detectable UMFA, at 7% versus 31%. It also showed significantly lower placental UMFA levels (study, 2026).
A 2025 meta-analysis of eleven randomised trials reached a similar conclusion: switching to an active folate form increased plasma and red cell folate and reduced UMFA. In women with a history of adverse pregnancy outcomes, it was also associated with higher subsequent pregnancy rates and fewer adverse outcomes (study, 2025). There’s even emerging evidence that everyday exposures can tip this balance. A 2025 analysis of the MIREC cohort looked at air pollution exposure in the third trimester. Higher exposure was associated with a lower proportion of active 5-MTHF and a higher proportion of UMFA in the blood (study, 2025). It’s a reminder that folate metabolism doesn’t happen in isolation from the rest of your health picture.
Choosing the Right Type of Folate for MTHFR in Pregnancy
Folate supplements differ far more than their labels suggest. This is a conversation I have with almost every pregnant or pregnancy-planning patient. Broadly, there are three forms you’ll come across:
Folic acid is the synthetic, oxidised form used in most standard prenatal vitamins and mandatory food fortification. It’s inexpensive and well-studied for neural tube defect prevention at a population level. It does require several enzymatic conversion steps, including via MTHFR, before your body can use it.
5-MTHF (levomefolic acid) is the bioactive form your body would otherwise have to make from folic acid or dietary folate. It bypasses the MTHFR conversion step entirely. That’s the main reason practitioners often choose it for people with reduced MTHFR enzyme function.
Folinic acid sits one step upstream of 5-MTHF and is another well-absorbed option. It’s sometimes preferred where a patient doesn’t tolerate 5-MTHF well.
The right choice depends on your genetics, your homocysteine and folate status on testing, your history, and how you respond and feel. That’s exactly why this decision benefits from individualised naturopathic assessment, rather than a one-size-fits-all prenatal vitamin off the shelf.
Methylation Support in Pregnancy: The Bigger Picture Beyond MTHFR
MTHFR gets the headlines, but it’s really just one gear in a much larger biochemical process called methylation. This is the process your body uses to switch genes on and off, build neurotransmitters, detoxify, and support your baby’s developing DNA. Folate is central to methylation because it feeds into one-carbon metabolism. This is the pathway that ultimately produces SAMe (S-adenosylmethionine), the body’s primary methyl donor.
According to PubMed, a 2025 review of nutriepigenomics in pregnancy describes how folate, vitamin B12, choline, vitamin D, omega-3 fatty acids and polyphenols all modify DNA methylation, histone modification and non-coding RNA activity in placental and foetal tissue (study, 2025). In other words, methylation support in pregnancy is a nutritional and genetic story. It goes well beyond a single gene, which is why we assess it as a whole system rather than testing MTHFR in isolation and calling it done.
Beyond MTHFR: Other Methylation Genes Worth Knowing
MTHFR is the most well-known methylation gene, but it isn’t the only one relevant to pregnancy. A few others come up regularly in nutrigenetic testing and are worth understanding.
MTR, MTRR and COMT
MTR and MTRR code for methionine synthase and its reductase enzyme. This is the step that directly recycles homocysteine back into methionine, using vitamin B12 as a cofactor. According to PubMed, a 2024 case-control study looked at women with unexplained recurrent pregnancy loss. It found the MTRR A66G variant (homozygous GG) significantly more common in this group than in fertile controls (study, 2024). A 2022 study of neural tube defect patients found both MTHFR C677T and MTR A2756G associated with lower red blood cell folate and increased NTD risk (study, 2022). A 2024 descriptive study of Kazakh women with preeclampsia found MTHFR polymorphisms present in around a quarter of cases, and MTRR variants in around 9%. It’s a reminder that this is a gene family worth assessing together, rather than in isolation (study, 2024).
COMT (catechol-O-methyltransferase) uses SAMe to clear dopamine, adrenaline and oestrogen. It draws on the same methyl-donor pool as folate metabolism, so COMT function is increasingly studied alongside MTHFR. Early research is exploring its role in oxidative stress pathways relevant to conditions like preeclampsia.
CBS and BHMT
CBS (cystathionine beta-synthase) sits at a fork in the pathway. It diverts homocysteine toward glutathione production instead of recycling it back to methionine. An overactive CBS pathway can influence how much homocysteine is available for the methylation cycle — one reason we don’t look at homocysteine or folate genetics in isolation.
BHMT (betaine-homocysteine methyltransferase) offers a backup route for recycling homocysteine, using betaine (derived from choline) rather than folate. This pathway is thought to handle roughly half of the body’s SAMe production via the liver. That’s part of why choline intake matters so much in pregnancy — more on that below.
None of these genes need to be memorised by you — that’s our job. Understanding that MTHFR sits within a network, not on its own, helps explain why a thorough nutrigenetic panel looks at more than one gene.
The B Group Vitamins and the Folate-Homocysteine Recycling Pathway
Folate doesn’t work alone. The entire folate-homocysteine recycling pathway depends on a team of B vitamins acting as cofactors. A shortfall in any one of them can bottleneck the whole system, regardless of how “clean” your folate supplement is.
Vitamin B12 is the direct partner of the MTR enzyme, required to convert homocysteine back to methionine. Low B12 can mimic or worsen the effects of an MTHFR variant. This is exactly why we test B12 status alongside folate and genetics rather than assuming folate is the whole story.
Vitamin B6 (as its active form, pyridoxal-5-phosphate) is required for the transsulfuration pathway that clears homocysteine via the CBS enzyme. It’s also needed for building neurotransmitters that draw on the same methylation resources. According to PubMed, a 2023 study from the MAASTHI pregnancy cohort in South India found maternal vitamin B6 levels significantly associated with infant birth weight. Impaired folate status nearly doubled the odds of low birth weight in the same cohort (study, 2023).
Riboflavin (B2) is a cofactor the MTHFR enzyme itself needs to function. This means that even with optimal folate intake and a favourable genetic profile, low B2 status can still limit how efficiently folate gets converted and used.
Choline, Betaine, Magnesium and Zinc
Choline and betaine feed the BHMT backup pathway described above. According to PubMed, a 2025 review explains that a choline-deficient diet reduces liver folate and hepatic SAMe, and raises homocysteine (study, 2025). In some contexts, choline and betaine intake can lower post-methionine-load homocysteine even more effectively than folate does. Choline is under-consumed in pregnancy far more often than most people realise, making it one of the more overlooked pieces of methylation support.
Magnesium and zinc round out the cofactor picture. This mineral is required for B6 to be activated into its usable form. It also supports hundreds of enzymatic reactions across the methylation and detoxification pathways. Zinc, meanwhile, supports numerous enzymes involved in DNA synthesis and repair alongside folate. Magnesium intake is another nutrient consistently found to fall short of pregnancy requirements. A large US study found close to half of pregnant women had intakes below the estimated average requirement (Bailey et al.).
Testing for MTHFR in Pregnancy: Why We Look Deeper
This is the part of MTHFR support in pregnancy that gets skipped most often. Testing is what turns “I have an MTHFR variant” from a source of anxiety into a specific, actionable plan. In our pregnancy consultations, a thorough work-up typically includes nutrigenetic testing, homocysteine, B12, B6, magnesium and a full thyroid panel.
Nutrigenetic Testing and Homocysteine
Nutrigenetic (nutrigenomic) testing looks at MTHFR (C677T and A1298C) alongside other methylation-relevant genes such as MTR, MTRR, COMT and CBS. This gives us a genetic map of where your methylation pathway may need more support.
Homocysteine is arguably the single most useful functional marker in this picture. Genetics tell us about potential, while homocysteine tells us about current function. According to PubMed, a 2026 study followed almost 30,000 singleton pregnancies. It found homocysteine positively associated with preterm birth risk, and the association strengthened as pregnancy progressed (study, 2026). Another 2025 study found that combining red blood cell folate with homocysteine testing gave a strong ability to identify women at risk of hypertensive disorders of pregnancy. The combined marker correctly identified the large majority of at-risk cases (study, 2025).
B12, B6, Magnesium and Thyroid Panel
Vitamin B12 and vitamin B6 testing tells us whether the cofactors your recycling pathway depends on are actually adequate, not just theoretically sufficient from diet.
Magnesium testing helps identify a genuinely common shortfall that can otherwise go unnoticed. We prefer red cell magnesium, which reflects tissue status far better than a standard serum test.
A full thyroid panel, including reverse T3, rounds out our pregnancy work-up. Thyroid function and methylation status are closely linked in pregnancy, since both influence energy metabolism, foetal neurodevelopment and each other. According to PubMed, a 2025 meta-analysis of 60 studies found subclinical or overt hypothyroidism present in around 17% of pregnancies overall. Each severity level was associated with a distinct pattern of adverse outcomes (study, 2025).
We include reverse T3 alongside TSH, free T4 and free T3 because it can highlight patterns of thyroid hormone conversion that a standard TSH-only screen misses. This is particularly relevant when someone is under physiological load, unwell, or nutrient-depleted, all of which are common in pregnancy. We’ll always be upfront that reverse T3 research specific to pregnancy is still an emerging area. That’s why we interpret it as one piece of a broader clinical picture, rather than a stand-alone diagnosis.
This depth of testing is what allows your naturopathic assessment to move from generic advice to a plan that’s actually built around your biochemistry. The same MTHFR result can mean quite different things for two different people. It depends on their B12, homocysteine, thyroid function and broader health picture.
Key Nutrients and Foods to Support MTHFR in Pregnancy
Alongside the right supplement strategy, food remains foundational. Here are the nutrients and foods I focus on most with MTHFR and methylation-support patients.
Folate-rich foods — leafy greens (spinach, silverbeet, kale), legumes, asparagus and broccoli provide natural dietary folate. It doesn’t carry the same UMFA considerations as synthetic folic acid.
Vitamin B12 sources — eggs, meat, fish and dairy for those who eat them; B12 needs particular attention and often supplementation for anyone following a plant-based diet.
Choline-rich foods — eggs (especially the yolk) are one of the richest everyday sources, alongside liver, fish and legumes.
Magnesium-rich foods — pumpkin seeds, leafy greens, legumes and wholegrains.
Vitamin B6 sources — poultry, fish, chickpeas, potatoes and bananas.
Riboflavin (B2) sources — dairy, eggs, almonds and mushrooms.
Food alone often isn’t enough to fully correct an existing shortfall in pregnancy, particularly where increased requirements and an MTHFR variant are both in the picture. Targeted, individually-dosed supplementation is where we go next.
Seeking Practitioner Support for MTHFR in Pregnancy
If you’ve had genetic testing that shows an MTHFR variant, please don’t try to interpret it alone or self-prescribe based on something you’ve read online. The same applies if you’re planning pregnancy with a history of recurrent loss, unexplained elevated homocysteine, or a family history of neural tube defects. MTHFR support in pregnancy is genuinely individual, depending on your specific variant, your homocysteine and B12 status, your diet, your thyroid function and your broader health history.
This is exactly the kind of picture we build with you in a naturopathic pregnancy consultation. We review your genetics and pathology together, identify where your methylation pathway needs support, and build a folate and nutrient strategy that’s right for your body, not a generic prenatal label. If any of this resonates with your own history, I’d encourage you to book a consultation. We can look at your picture properly, working alongside your GP or obstetrician as part of your overall pregnancy care.
Frequently Asked Questions
Does having MTHFR mean I need a special prenatal vitamin?
Not automatically, but it’s worth reviewing. Many people with an MTHFR variant benefit from a prenatal that uses 5-MTHF or folinic acid instead of, or alongside, folic acid. The right choice depends on your specific variant, your homocysteine and B12 status, and your overall health picture — best assessed individually.
Is MTHFR the only gene I should worry about?
No. MTHFR is the best-known methylation gene, but MTR, MTRR, COMT and CBS all play a role in the same pathway. A thorough nutrigenetic panel looks at these together rather than MTHFR in isolation.
What is unmetabolised folic acid, and should I be worried about it?
Unmetabolised folic acid (UMFA) is circulating folic acid that hasn’t been fully converted into its active form. It’s more likely to build up when folic acid intake exceeds your body’s conversion capacity, which can happen more easily with reduced MTHFR function. Choosing an active folate form, guided by your practitioner, is how we mainly address this.
What testing is involved in assessing MTHFR and methylation in pregnancy?
A thorough work-up typically includes nutrigenetic testing (MTHFR and related genes), homocysteine, vitamin B12, vitamin B6, magnesium, and a full thyroid panel including reverse T3. Together these give us both the genetic picture and the functional, current-status picture.
Can I address MTHFR and methylation support through diet alone?
Diet is foundational — folate-rich vegetables, B12 and choline sources, magnesium-rich foods — but pregnancy significantly increases requirements. Food alone often can’t fully correct an existing shortfall, particularly alongside an MTHFR variant. Most patients need a combination of dietary focus and individually-dosed supplementation.
References
- Yang & Li. The roles of folate, MTHFR genetics, and vitamin B12 in pregnancy outcomes. Frontiers in Nutrition, 2026. https://doi.org/10.3389/fnut.2026.1785263
- RCT of 6S-5-MTHF versus folic acid in prenatal multivitamins. Frontiers in Nutrition, 2026. https://doi.org/10.3389/fnut.2026.1679067
- Meta-analysis of active folate form on folate status and pregnancy outcomes. Medicine, 2025. https://doi.org/10.1097/MD.0000000000046564
- Air pollution and folate/UMFA status in pregnancy (MIREC cohort). Current Developments in Nutrition, 2025. https://doi.org/10.1016/j.cdnut.2025.107617
- MTHFR polymorphisms and recurrent pregnancy loss. International Journal of Molecular Sciences, 2026. https://doi.org/10.3390/ijms27073112
- MTHFR 677TT and hyperhomocysteinemia in unexplained recurrent pregnancy loss. Thrombosis Research, 2026. https://doi.org/10.1016/j.thromres.2026.109687
- MTHFR and MTRR variants in recurrent spontaneous abortion. Journal of Maternal-Fetal & Neonatal Medicine, 2025. https://doi.org/10.1080/14767058.2025.2505769
- MTRR and MTR polymorphisms and recurrent pregnancy loss. Molecular Biology Reports, 2024. https://doi.org/10.1007/s11033-024-09860-4
- MTHFR and MTR polymorphisms, RBC folate and neural tube defects. Journal of Indian Association of Pediatric Surgeons, 2022. https://doi.org/10.4103/jiaps.jiaps_29_22
- Folate metabolism gene polymorphisms in preeclampsia. Biology, 2024. https://doi.org/10.3390/biology13090648
- Nutriepigenomics in pregnancy: folate, B12, choline, vitamin D and DNA methylation. Journal of Perinatal Medicine, 2025. https://doi.org/10.1515/jpm-2025-0289
- Maternal B6 and folate status and birth outcomes (MAASTHI cohort). Nutrients, 2023. https://doi.org/10.3390/nu15071793
- Choline, betaine and the BHMT pathway in one-carbon metabolism. Nutrients, 2025. https://doi.org/10.3390/nu17152495
- Bailey et al. Total usual nutrient intakes among US women. JAMA Network Open, 2019. https://doi.org/10.1001/jamanetworkopen.2019.5967
- Homocysteine and pregnancy outcomes across gestation. BMC Pregnancy and Childbirth, 2026. https://doi.org/10.1186/s12884-026-09545-9
- RBC folate and homocysteine testing in hypertensive disorders of pregnancy. International Journal of Women’s Health, 2025. https://doi.org/10.2147/IJWH.S568633
- Hypothyroidism prevalence and outcomes in pregnancy: meta-analysis. Indian Journal of Medical Research, 2025. https://doi.org/10.25259/IJMR_2554_2025
According to PubMed, the studies referenced above were retrieved from the PubMed database; DOI links are provided for each source above.
