Shaw et al. (33) performed a candidate gene screen of these 118 SNPs in a Californian population, and found a modest association between spina bifida (NTD) risk and SNPs in seven genes related to folate metabolism [BHMT, MTHFD1, MTHFD2, MTHFR, MTRR, cystathionine-β-synthase (CBS), and thymidylate synthase (TYMS)]. This evidence concerns the gene TYMS and spina bifida.