Pregnancy multivitamins are a waste of money because most mothers-to-be do not need them, according to researchers.

In Drug and Therapeutics Bulletin, researchers say they looked at all evidence and found supplements did not boost the health of mothers and babies.

But pregnant women should make sure they take folic acid and vitamin D, as well as eating a well-balanced diet, they add. Supplements-makers said some women were not getting enough nutrients.

The researchers said folic acid had the strongest evidence to support its use — taking 400 micrograms a day can protect against abnormalities called neural tube defects in the developing baby. Vitamin D — 10 micrograms a day — is recommended for healthy bones in the mother and baby. A supplement that can be dangerous in pregnancy is vitamin A. Too much can harm the baby.

The researchers said pregnant women might feel coerced into buying expensive multivitamins in order to give their baby the best start in life. "The only supplements recommended for all women during pregnancy are folic acid and vitamin D, which are available at relatively low cost," they said.