Higher Parental Vitamin B12 Levels May Be Associated With Fewer Birth Defects, Study Finds

New research suggests that higher vitamin B12 levels in parents before conception may be associated with a lower prevalence of birth defects, while maternal folate may also play an important role.

Nutrition before and during pregnancy has long been considered an important part of supporting healthy fetal development. Folate is particularly well known for its role in reducing the risk of certain birth defects. However, new research suggests that another important nutrient, vitamin B12, may also deserve greater attention when considering nutritional health before pregnancy.

A new prospective cohort study published in the Annals of Internal Medicine examined the relationship between parental vitamin B12 levels, maternal folate levels and the prevalence of birth defects. The findings suggest that higher vitamin B12 concentrations in both mothers and fathers before conception were associated with lower predicted rates of birth defects in their children.

The research also found associations involving maternal red blood cell folate and vitamin B12 during early pregnancy.

What Did the Study Examine?

Researchers led by Hongyan Chen, Ph.D., of the Children's Hospital of Fudan University in Shanghai, evaluated nutritional biomarkers in thousands of couples and pregnant women.

One part of the study included 3,032 couples, among whom 73 birth defect cases were identified. Biomarkers were collected within four months before conception, allowing researchers to investigate the nutritional status of both parents during the period immediately before pregnancy.

A second group included 17,765 women, with 327 identified birth defect cases. These participants had biomarkers measured at four months of pregnancy or earlier.

This approach allowed researchers to examine nutritional factors not only in mothers but also in fathers before conception. That is notable because much of the previous research surrounding nutrition and birth defects has focused primarily on maternal health.

Higher Maternal Vitamin B12 Was Associated With Lower Predicted Prevalence

The researchers identified a dose-response pattern involving maternal vitamin B12 levels before conception.

Among women with the lowest vitamin B12 concentrations, defined in the study as below 148 pmol/L, the predicted prevalence of birth defects was approximately 49.6 cases per 1,000 pregnancies.

At the highest vitamin B12 category, defined as 590 pmol/L or higher, the predicted prevalence fell to approximately 16.2 cases per 1,000 pregnancies.

This does not mean that increasing vitamin B12 intake will necessarily prevent birth defects. Rather, the findings show an association between vitamin B12 status before conception and the observed statistical likelihood of birth defects within the study population.

Researchers also observed a similar relationship for paternal vitamin B12, although the pattern was less pronounced.

Fathers' Vitamin B12 Status May Also Matter

One of the more interesting aspects of the research is its focus on paternal nutrition.

The predicted prevalence of birth defects decreased from approximately 55.5 to 24.0 cases per 1,000 pregnancies as paternal preconception vitamin B12 levels increased across the categories examined.

Traditionally, pregnancy nutrition advice has centered heavily on the mother. While maternal nutrition remains extremely important, this research adds to growing scientific interest in the potential contribution of paternal health and nutrition before conception.

The biological reasons behind this association require further investigation. Researchers cannot conclude from this observational study that paternal vitamin B12 directly prevents birth defects. However, the findings suggest that nutritional status in both parents may be worth considering when studying factors that influence early fetal development.

Folate Remains an Important Nutrient

The study also investigated red blood cell folate, a measure that can provide information about longer-term folate status.

The researchers found some associations between higher folate concentrations and lower predicted birth defect prevalence. However, the patterns for preconception parental red blood cell folate were described as imprecise.

Among women whose biomarkers were measured during early pregnancy, predicted birth defect prevalence was lower at red blood cell folate concentrations between 906 and 1,131 nmol/L compared with levels below 453 nmol/L.

These findings add to the extensive scientific interest in folate and pregnancy. Folate is essential for cell division and DNA synthesis, processes that are especially important during the earliest stages of fetal development.

Vitamin B12 and Folate Work Within a Larger Nutritional Picture

Vitamin B12 and folate are closely connected in several biological processes, including those involved in DNA production and normal cell function.

Vitamin B12 is naturally found in foods such as meat, fish, eggs and dairy products, while some plant-based foods are fortified with the nutrient. People following vegetarian or vegan diets may need to pay particular attention to their vitamin B12 intake because naturally occurring B12 is primarily found in animal-derived foods.

Folate can be obtained from foods including leafy green vegetables, beans, peas and certain fruits. Folic acid, the synthetic form of folate used in supplements and food fortification, is also widely recommended before and during pregnancy.

However, nutritional needs vary from person to person. Taking more of a vitamin is not automatically better, and excessive supplementation can sometimes be inappropriate or harmful.

What Do These Findings Mean for People Planning a Pregnancy?

The study provides another reason to consider nutritional health before conception rather than waiting until pregnancy has already begun.

For people planning a pregnancy, maintaining a balanced diet and discussing prenatal vitamins or supplements with a healthcare professional can help identify potential nutritional gaps. A clinician may also recommend blood tests when there is a reason to suspect a vitamin deficiency.

Importantly, the study does not establish that vitamin B12 supplementation prevents birth defects. It was an observational study that identified statistical associations between biomarker levels and birth defect prevalence.

Other factors may also influence pregnancy outcomes, including genetics, underlying health conditions, medications, environmental exposures, maternal age and overall nutritional status.

More Research Is Needed

The authors say their findings expand research that has historically concentrated on maternal folate. Their results suggest that nutritional status around conception may be broader than previously considered and could include paternal vitamin B12 status.

Future studies will be needed to determine whether vitamin B12 has a direct biological effect on birth defect risk and whether correcting a vitamin B12 deficiency before conception changes pregnancy outcomes.

Randomized clinical trials and additional studies involving different populations could provide a clearer understanding of the relationship.

The Bottom Line

New research suggests that higher vitamin B12 levels in both mothers and fathers before conception may be associated with a lower predicted prevalence of birth defects. The study also identified associations involving maternal folate and vitamin B12 during early pregnancy.

The findings are interesting because they highlight the potential importance of nutritional health for both parents before pregnancy. They also reinforce the broader message that adequate nutrition is an important component of reproductive and prenatal health.

At the same time, the results should not be interpreted as proof that taking vitamin B12 supplements will prevent birth defects. Anyone planning a pregnancy should speak with a qualified healthcare professional about diet, prenatal vitamins, existing medical conditions and individual nutritional needs.

Source: Chen H, et al. Study published online September 1, 2026, in the Annals of Internal Medicine.

Medical Disclaimer: This article is intended for general informational and educational purposes only. It does not constitute medical advice, diagnosis or treatment. Research findings describe associations at the population level and may not predict what will happen in an individual pregnancy. Nutritional requirements and pregnancy risks can vary substantially between individuals. Do not start, stop or change vitamin supplements based solely on this article. Speak with your doctor, midwife, dietitian or other qualified healthcare professional for personalized advice, particularly when planning pregnancy or during pregnancy.