MTHFR Testing During Pregnancy

Women who are pregnant or planning pregnancy may be wondering if they should be tested for MTHFR genetic mutations. Several studies have linked pregnancy complications with MTHFR enzyme deficiency, especially in those with MTHFR C677T. MTHFR is also associated with unmetabolized folic acid syndrome (UMFA) due to the body’s inability to fully process folic acid, which may mean that standard folic acid supplementation during pregnancy is unsuitable for some people.¹

However, MTHFR genotyping is not routinely tested in pregnancy, even for patients affected by thrombophilia (tendency for blood clots) or recurrent pregnancy loss.²

Research published in 2026 has recommended both screening for MTHFR as well as personalized prenatal nutrition plans for pregnant women rather than universal folic acid supplementation.³ These recommendations are based on evidence that there is a higher prevalence of MTHFR variants in pregnancies with complications or recurrent miscarriages.⁴ MTHFR is also a risk factor for cardiovascular issues such as high homocysteine and thrombosis, which can have serious complications in pregnancy.⁵

A recent 2026 review investigating the impact of folate, MTHFR genetics, and vitamin B12 on pregnancy outcomes recommended “pre-conception or early-pregnancy screening” alongside other genetic and nutritional factors. They stated that clinicians should assess and maintain a woman’s folate levels and provide an individualized preventive strategy with personalized nutrition rather than the current population-based recommendation.⁶

Fetal malformations are positively correlated with MTHFR enzyme deficiency, and MTHFR reduces the body’s ability to metabolize folic acid. In a 2023 review, researchers have suggested that folic acid prescription in pregnancy should be regulated, and that healthcare professionals conduct a comprehensive assessment of a pregnant woman’s health, including nutritional status.⁷

Clinical studies have confirmed that neural tube defects and elevated homocysteine are linked to MTHFR variants, and this is associated with numerous pregnancy complications, including recurrent pregnancy loss (RPL), preeclampsia (PE), preterm delivery, placental abruption, fetal growth restriction (FGR), and gestational diabetes mellitus (GDM).⁸

Women with homozygous MTHFR C677T have an increased risk of having a child with a neural tube defect (this risk increases if the fetus is also homozygous). If the woman also has high homocysteine, the risk of venous thrombosis or recurrent pregnancy loss also increases.⁹

Testing for MTHFR gene variants during pregnancy causes no harm or risk to the mother or fetus. It requires only a saliva swab (taken from the inside of the cheek) or a blood test. It is no more complicated than a pregnancy test.

The American College of Obstetricians and Gynecologists (ACOG) and other medical bodies have stated that MTHFR genotyping should not be ordered as part of the clinical evaluation for thrombophilia, recurrent pregnancy loss, or at-risk family members.

An estimated 60–70% of individuals will have at least one MTHFR variant, which affects the body’s ability to convert folic acid to its active form.¹⁰

It is important to note that the MTHFR variant is very common, and the majority of women with some form of MTHFR variant still have a healthy pregnancy. Complications are mainly associated with high homocysteine, low folate, and low B12, so it is more important to test for - and treat - these factors instead. 

A personalized prenatal nutrition plan, along with monitoring of folate and B12, can then be created.