In spina bifida case studies, MTHFR C677T variant was clearly reported as associated gene or risk factors in Irish (451 spina bifida patients), mixed USA, mixed UK, and Italian cohort but not in other 180 Dutch patients (Table 3), while A1298C variant was reported with no association to spina bifida cases in Italian, Mexican (Yucatan), and Dutch population (Table 3). MTHFR is the most studied human spina bifida gene, as its role in folate one-carbon metabolism fits into a clear mechanism of NTD. Here, MTHFR is linked to spina bifida.