According to data published in the British Medical Journal, folic acid supplements during early pregnancy could reduce the risk of cleft lip in infants by as much as 33 percent.

While the link between folate deficiency and neural tube defects such as spina bifida and anencephaly are well-established, this is the first study to suggest a link between folate deficiency and cleft lip.

This retrospective study was done in Norway where the incidence of facial clefts is among the highest in Europe.   Infants born between 1996 to 2000 were identified - 377 with cleft lip (with or without cleft palate), 196 with cleft palate only, and 763 healthy controls.

Mothers were asked to recall their diet during the first three months of pregnancy, whether they took vitamins or folic acid supplements, and if so, when and how often.   After adjusting for smoking and other confounding factors, the researchers reported that folic acid supplementation of 400 micrograms or more a day was associated with a 40 reduced risk of cleft lip with or without cleft palate.
Becauce folic acid alone did not appear to provide protection against cleft palate, the researchers concluded that their study alone cannot show that folic acid prevents cleft palate but the data suggest a protective effect that merits further investigation.