When people hear about nutrition before pregnancy, the focus is usually on women. New research suggests fathers may belong in that conversation, too.
In a large prospective study in China, higher vitamin B12 levels in both mothers and fathers before conception were associated with a lower prevalence of birth defects in their children. Higher folate levels in mothers during early pregnancy were also linked to lower risk. The findings do not prove that raising vitamin B12 or folate levels will prevent birth defects, but they suggest the nutritional status of both parents around conception may be worth a closer look.
The study, published in Annals of Internal Medicine, used data from the Shanghai Preconception Cohort. Researchers studied 3,032 couples who had blood drawn within four months before conception. They also analyzed blood samples from 17,765 women taken during the first four months of pregnancy.
Instead of relying on participants to remember what they ate or which supplements they used, researchers measured vitamin B12 and folate levels in their blood. They then looked at birth defects identified among live births, stillbirths and pregnancies that ended because of fetal abnormalities.
The clearest new finding involved vitamin B12. Higher levels before conception were associated with a lower prevalence of birth defects whether those higher levels were found in the mother or the father.
That paternal connection stands out because most nutrition guidance around conception has traditionally centered on the person who will become pregnant.
The study also reinforced the importance of folate during early pregnancy. Women with adequate levels of folate stored in their red blood cells had a lower predicted prevalence of birth defects. Red blood cell folate is one way researchers can assess longer-term folate status rather than simply measuring what is circulating in the blood at a single moment.
Folate is already a well-established part of preconception and pregnancy care because adequate intake before and during early pregnancy helps reduce the risk of neural tube defects. The new findings do not change those recommendations. Instead, they raise a broader question about whether vitamin B12 and paternal nutrition deserve more attention as well.
The results should not be read as a reason for prospective parents to start taking large amounts of vitamin B12.
This was an observational study, not a clinical trial. Researchers found that people with higher B12 levels tended to have pregnancies with fewer birth defects, but they did not give participants B12 supplements and test whether those supplements changed outcomes.
People with higher B12 levels may also differ in other ways, including their overall diets, supplement use, health or other factors that could influence pregnancy outcomes. That means the study cannot establish that vitamin B12 itself caused the lower risk.
It also cannot tell prospective parents how much B12 they should consume. The researchers measured blood levels rather than testing a particular supplement dose or dietary plan.
Still, the findings add to a growing interest in health before conception as something that involves both parents. Future research will be needed to determine whether the B12 associations appear in other populations and whether improving B12 status before pregnancy can actually reduce birth defect risk.
The study was supported by the National Key Research and Development Program of China, the National Natural Science Foundation of China and the Chinese Academy of Medical Sciences.