Folic acid is the synthetic form of folate, a B vitamin, and is found in many prenatal supplements and fortified foods, such as cereals and pastas. It is crucial for cell proliferation, which is in overdrive during pregnancy. Insufficient folate during fetal development has long been linked to neural tube defects, such as spina bifida and anencephaly. Multiple studies link prenatal folic acid supplementation to lowered odds of autism, even when pregnant women take epilepsy medications, such as valproic acid, that appear to increase those chances. Too much folic acid may also increase the odds of autism, though. Excess folic acid supplementation had similar effects as folic acid deficiency in one mouse study, for example. The experimental mice in this study ingested 10 times as much folic acid as controls. These results do not mean folic acid should be avoided — just that it should be taken in recommended quantities.