NOS3 and persistent fetal circulation syndrome: Variants in NOS3, particularly c.894T>G and c.-149+1691C>T, have been associated with adverse neonatal outcomes, including impaired cerebral blood flow and increased risk of IVH [52], ROP requiring treatment [53], perinatal HIE (G allele of c.894T>G), and PPHN (T/C genotype and C allele of c.-149+1691C>T) [54].