MTHFR and Rare hereditary thrombophilia: On the other hand, Factor V Leiden (p < 0.001), MTHFR A1298C homozygous (p < 0.001), MTHFR C677T homozygous (p < 0.001), PAI-I deficiency (p < 0.001), and AT III deficiency (p < 0.001) were thrombophilia mutations with significant impact over the SGA occurrence later in pregnancy (Table 1).