Pregnant women who take folic acid can dramatically cut the chances of their baby having a harelip, say researchers.
Mothers-to-be are already advised to take supplements of the B vitamin to help prevent conditions such as spina bifida.
But a study has found folic acid was more effective than previously thought, reducing the risk of facial clefts by a third.
One in 1,000 babies born in the UK has the condition, but researchers found the lowest risk was among women who combined a folate-rich diet, multivitamins and daily folic acid supplement.
The Department of Health recommends women planning a pregnancy increase their intake of folic acid and also take a daily supplement. They are advised to continue taking folic acid for the first three months of a pregnancy.
Researchers examined the effects of folic acid on facial clefts in Norway, which has one of the highest rates in Europe. They studied babies born between 1996 and 2001, of whom 377 had a harelip, 196 had a cleft palate only and 763 were healthy controls.
The study found that taking folic acid supplements reduced the risk of a harelip, with or without a cleft palate, by a third.
Diets rich in high-folate foods such as fruit and vegetables also helped reduce the risk, according to the study, published online in the British Medical Journal.
Source - Daily Mail