Observations on the prevention of cleft palate in dogs by folic acid and potential relevance to humans.

Folic acid has been shown to prevent neural tube defects in humans, but its effects on other defects is unknown. In a consistent breeding programme of Boston terrier dogs started in 1974, folic acid supplementation (5 mg/day) was introduced in 1981. The frequency of cleft palate fell from 9/51 (17.6%) without folic acid to 8/191 (4.2%) after its introduction, giving a reduction of 76% (95% confidence limits 42%-90%, p = 0.003).