Fathers’ B12 levels may lower birth defect risks

New research suggests that a father’s vitamin B12 levels before conception may play a role in reducing birth defects in children, alongside the well-documented benefits of maternal folate intake. A study from China found that higher B12 levels in both prospective mothers and fathers were linked to lower rates of birth defects, challenging the long-held assumption that prenatal nutrition is solely a woman’s responsibility.

How the study measured nutritional impact

The research, led by scientists at the Children’s Hospital of Fudan University in Shanghai, analyzed blood samples from two groups. The first included 3,032 couples who provided samples within four months before conception. The second group consisted of 17,765 women tested by the fourth month of pregnancy. Researchers measured vitamin B12 and red blood cell folate, an indicator of longer-term folate status, and tracked pregnancies for birth defects in live births, stillbirths, and cases where fetal abnormalities were detected.

The data showed a clear trend: among women, predicted birth defect rates dropped from 49.6 per 1,000 pregnancies in those with the lowest preconception B12 levels to 16.2 per 1,000 in those with the highest. For fathers, the decline was similarly sharp, falling from 55.5 to 24 per 1,000 pregnancies across the lowest to highest B12 categories. The study also confirmed that adequate maternal folate levels after conception remained beneficial, though the focus on paternal B12 was novel.

This isn’t the first time nutrition before conception has been linked to pregnancy outcomes. For years, public health guidelines have emphasized folic acid for women to prevent neural tube defects. But the new findings suggest that sperm health, potentially influenced by a father’s diet, may also factor into reducing risks. The biological mechanisms aren’t yet fully understood, but B12 is known to support DNA synthesis and sperm production, which could indirectly affect fetal development.

What the findings mean for couples planning pregnancy

The study doesn’t prove that B12 supplements alone can prevent birth defects; it only establishes an association. Still, it reinforces the idea that preparing for a healthy pregnancy requires attention from both partners. Unlike folic acid, which has been heavily promoted for women, B12 hasn’t been a focus of preconception advice for men. The researchers noted that couples shouldn’t rush to high-dose supplements without guidance, but the results suggest a broader conversation about nutrition before conception is needed.