The study aimed to assess the association of nucleated red blood cells (NRBC), a surrogate of intrauterine hypoxia, and elevated pulmonic vascular resistance (E-PVR) and oxygen requirement after minimally invasive surfactant therapy (MIST).
 Retrospective study of a cohort of preterm neonates that received MIST in a single unit.
 NRBC were measured in 65 of 75 (87%) neonates administered MIST during the period. In total, 22 of 65 (34%) infants had pre-MIST echocardiography (ECHO).Neonates with elevated NRBC (predefined as >5 × 10/L,  = 16) required higher post-MIST fraction of inspired oxygen (FiO) than neonates with normal NRBC (<1 × 10/L,  = 17; FiO= 0.31 ± 0.10 and 0.24 ± 0.04, respectively,  = 0.02).NRBC correlated positively with % of time in right to left ductal shunt (r = 0.51,  = 0.052) and inversely with right ventricular stroke volume (r = -0.55,  = 0.031) and time to peak velocity to right ventricular ejection time ratio (r = -0.62,  < 0.001).
 Elevated NRBC are associated with elevated FiO after MIST and elevated E-PVR. Intrauterine hypoxia may impact postnatal circulatory adaptations and oxygen requirement.
· Post-MIST FiO2 requirements are significantly higher in infants with elevated NRBC.. · NRBC correlates positively with elevated PVR in neonates requiring.. · Intrauterine hypoxia may play a role in postnatal circulatory adaptations in neonates with RDS..

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