A study published in the Annals of Internal Medicine by researchers at Fudan University in China has found that vitamin B12 levels in both parents before conception are associated with a reduced risk of birth defects. The study included over 3,000 couples who provided blood samples within four months before conception, as well as 17,765 women tested at four months' gestation or earlier. Researchers measured levels of vitamin B12 and B9 (folate) and examined their relationship with birth defects in live births, stillbirths, and pregnancies ending due to fetal abnormalities.