Effects of 100% oxygen during deferred cord clamping on oxidative stress markers: a sub-study of a randomized controlled trial.

We sought to evaluate oxidative changes in premature infants receiving 100% oxygen compared with 30% during deferred cord clamping (DCC). Premature infants born at 220/7 to 286/7 weeks received DCC in conjunction with either 30% (LO Group) or 100% (HI Group) oxygen. Blood was extracted from a preserved umbilical segment and a postnatal sample was collected from umbilical vascular lines within two hours of birth. Reduced-to-oxidized glutathione (GSH/GSSG) ratios were analyzed using liquid chromatography coupled to tandem mass spectrometry. Sixty-eight infants had data available for analysis. The median (IQR) gestational age of infants was 264/7 (246/7, 282/7) weeks in both groups. Among infants receiving 100% versus 30% oxygen, median (IQR) GSH/GSSG ratio were not statistically different in arterial cord blood [7.5 (0.6, 290) vs 37 (1.1, 265), p = 0.52] or venous cord blood [8.4 (2,50) vs 76 (5, 210), p = 0.12] or postnatal samples [14 (2, 290) vs 8 (2, 280), p = 0.98)]. Briefly providing 30% vs. 100% oxygen for 90 seconds during DCC showed no significant difference in GSH/GSSG ratios, but redox effects remain unclear given variability, sample size and limited power. Further studies are needed to ascertain potential oxidative damage during neonatal resuscitation and deferred cord clamping. THIS TRIAL IS REGISTERED ON CLINICALTRIALS. NCT04413097 IMPACT: The effect of oxygen administration during deferred cord clamping on redox status is unclear due to large variability in GSH and GSSG values and small sample size. These data provide some insights about umbilical arterial and venous oxygen levels and the effect of placenta on GSH/GSSG in preterm infants. Further basic and clinical studies are needed to better ascertain the potential for oxidative damage during neonatal resuscitation and deferred cord clamping.