Charity Shine said it is now believed that taking vitamin B12 alongside folic acid may be more effective than taking folic acid alone
Mothers-to-be should take vitamin B12 to prevent their children developing birth defects such as spina bifida, a charity has said.
New research suggests that taking the supplement alongside folic acid will help prevent neural tube defects (NTDs).
Women who are trying to conceive, or in the first 12 weeks of pregnancy, are already advised to take 400 micrograms of folic acid each day.
But charity Shine said it is now believed that taking vitamin B12 alongside folic acid may be more effective than taking folic acid alone.
Shine, which helps individuals and families affected by spina bifida and hydrocephalus, is recommending that pregnant women, and those trying to conceive, should take 2.5mcg of B12 once a day with a meal.
Jackie Bland, chief executive officer at Shine, said: "NTDs are a serious health threat which can lead to enormous challenges and painful decisions.
"The most serious form, anencephaly, means that the baby will not live long beyond birth, and many babies born with spina bifida face a life with serious, multiple disabilities.
"Shine is committed to the primary prevention of NTDs and as such it is our duty to make women aware of the potential benefits of B12."
Spina bifida is a series of birth defects that affect the development of the spine and central nervous system.