Risk of fetal deformities increases when fathers are also deficient in these two vitamins
A recent Chinese study published in the journal Annals of Internal Medicine revealed that fathers’ levels of vitamin B12 and vitamin B9 (folic acid) at the time of conception and pregnancy are directly associated with an increased likelihood of birth defects in the fetus, whereas previous research had focused primarily on deficiencies in mothers alone.
Researchers from Fudan University in China explained that low vitamin levels in fathers around the time of conception may raise the risk of birth defects in the fetus, alongside the well-established role of maternal nutrition. The study included more than 3,000 couples who provided blood samples within four months before conception, as well as 17,765 women who underwent testing during the first four months of pregnancy or earlier.
Among mothers, the risk of birth defects declined steadily as levels of these two vitamins increased. Among couples, the risk decreased with initial increases in vitamin levels before stabilizing at relatively high levels. The study authors noted that these findings highlight the importance of nutrition for both fathers and mothers before pregnancy and during its early stages.
The results provided precise indicators regarding the relationship between vitamin levels and defect rates, including:
• A decline in the expected rate of birth defects among mothers from 49.6 to 16.2 cases per 1,000 pregnancies between the highest and lowest categories of vitamin B12 and B9 levels.
• A similar, though less pronounced, decline among couples between the highest and lowest categories of the same vitamin levels.
• An additional reduction in the expected rate of birth defects associated with adequate folic acid (vitamin B9) levels in mothers at the beginning of pregnancy.
The researchers explained that vitamin B12, found in poultry, meat, fish, and dairy products, plays a fundamental role in the production and maintenance of healthy nerve cells, as well as in the formation of red blood cells and DNA, which explains its direct impact on fetal growth in the early stages of pregnancy.
In this context, previous research has pointed to additional benefits extending to later stages of the child’s life. A 2026 systematic review encompassing 22 studies concluded that adequate vitamin levels in mothers are consistently associated with improved performance in language, memory, and cognitive abilities in children.
The study authors emphasized that these findings call for a reevaluation of health awareness programs to include fathers alongside mothers during the preconception planning stage, rather than limiting dietary recommendations to pregnant women alone, which could potentially contribute to a broad reduction in birth defect rates in the future.
