MTHFR and Patent ductus arteriosus: Two statistically significant associations were observed for the MTHFR rs1801133T variant: the CT heterozygous genotype was associated with a 1.67-fold-higher risk of developing BPD (vs. CC; p = 0.017), and the TT homozygous genotype was associated with a 2.19-fold-higher risk of developing PDA (recessive model; p = 0.028).