There has been growing evidence that maternal obesity is associated with an increased risk of congenital malformations, particularly of neural tube defects. Two new studies confirm this relationship and indicate that it is independent of possible covariant confounders such as maternal age, socioeconomic status, education, smoking, and vitamin intake, including folic acid. There is a suggestion that folic acid loses its protective benefit in overweight and obese mothers. These new findings add to a long list of obstetric morbidities, and show a steep gradient with increasing maternal fatness and point to the urgent need to prevent excess weight gain in young women.