EDN1 and retinopathy of prematurity: Markers of respiratory morbidity, sepsis, and interestingly not hsPDA, which itself is associated with MR-proANP and CT-proET1, were no longer associated with the development of any stage ROP and ROP ≥ stage II after adjustment for co-factors.22 This suggests that ANP and ET1 might have an intrinsic effect on retinal vascularisation and ROP development but involved mechanisms are not fully understood.