Vitamin B12, found in poultry, meat, fish, and dairy, is essential for nerve health, red blood cell production, and DNA synthesis. A new study from Fudan University in China suggests that the vitamin's levels in both parents before conception may influence the likelihood of birth defects.
The research, published in the Annals of Internal Medicine, tracked over 3,000 couples who provided blood samples within four months before conception, plus nearly 18,000 women tested at four months' gestation or earlier. The team measured B12 and folate (vitamin B9) levels and analyzed their association with birth defects in live births, stillbirths, and pregnancies terminated due to fetal abnormalities.
Results showed that the predicted prevalence of birth defects fell from 49.6 to 16.2 cases per 1,000 pregnancies when comparing mothers with the highest versus lowest B12 levels. A similar but smaller effect was observed for fathers. For mothers, the risk decreased steadily with rising B12 levels; for fathers, the risk dropped initially but leveled off once they reached moderately high levels.
These findings underscore a point often overlooked: the father's vitamin B12 status around conception may also affect the risk of birth defects. The authors argue that both paternal and maternal nutrition before conception and during early pregnancy are important.
Why paternal B12 matters
Previous research has largely focused on maternal nutrition, but this study highlights the role of paternal health. The researchers suggest that B12 deficiency in fathers could influence sperm quality or epigenetic factors that affect fetal development. This adds to a growing body of evidence that preconception health is a shared responsibility.
In addition to B12, the study found that mothers with adequate red blood cell levels of folate in early pregnancy also had a lower predicted prevalence of birth defects. Folate is already widely recommended for pregnant women, but this new data reinforces the need for both partners to maintain adequate levels.
The study's findings align with earlier research showing benefits later in life for children whose mothers had sufficient B12 during pregnancy. A separate 2026 systematic review of 22 studies concluded that adequate maternal B12 status is consistently associated with better language, memory, and cognitive performance in children.
While the study is observational and cannot prove causation, it adds weight to calls for public health strategies that address nutrition in both parents before conception. As research on parental health and offspring outcomes continues to expand, this study offers a practical message: ensuring adequate B12 intake—through diet or supplements—may be a simple step for couples planning a family.
For European readers, where diets vary widely, the findings are relevant. In countries like Germany and France, meat and dairy consumption is common, but vegetarian and vegan populations may be at higher risk of deficiency. Public health campaigns across the EU could consider emphasizing B12 for both men and women when discussing preconception care.
The study also raises questions about how to best measure and interpret B12 status. The researchers used blood levels, but functional markers might provide a more accurate picture. Future research could explore whether targeted supplementation for fathers yields measurable benefits.
As the scientific community continues to explore the links between nutrition and birth outcomes, this study serves as a reminder that health before conception is a family affair. For couples planning a pregnancy, checking B12 levels might be as important as checking folate.
