How are babies born without a brain?
Know your databases! This is just the query fit for OMIM.

http://omim.org/entry/206500


  Anencephaly is considered an extreme form of neural tube defect
  (182940), which has been associated with variation in several genes.
  The entity described here is believed to show autosomal recessive
  inheritance.


The genes are those associated with neural tube effects, i.e., VANGL1, T, CCL1, and FUZ. See also folate-sensitive neural tube defects.

http://omim.org/entry/182940

The folate evidence was so convincing that the US/Canada in the 1990s introduced folate supplementation in all bread, flour, and cereal products. Today, US/Canada have a lower incidence of NTD (neural tube defects) than Europe, where folate supplementation is completely left to one's choice (and if women actually care they take it too late).