The absence of the fetal cranial vault in anencephaly is shown here. The incidence of anencephaly, one form of neural tube defect, has been reported to occur as frequently as 1 to 5 in 1000 live births in the past. However, dietary folic acid supplementation by mothers-to-be before and during pregnancy can reduce the incidence of such birth defects. The rate of anencephaly is now less than 1 in 10,000 live births in some places.