Intrauterine Hyperoxemia and Risk of Neonatal Morbidity

Abstract

Objective To test the hypothesis that intrauterine hyperoxemia is associated with an increased risk of neonatal morbidity. Methods This was a secondary analysis of a prospective study of singleton, non-anomalous deliveries at or beyond 37° weeks at an institution with universal umbilical cord gas policy from 2010 to 2014. The primary outcome was a composite of neonatal morbidity including neonatal death, meconium aspiration syndrome, intubation, mechanical ventilation, hypoxic-ischemic encephalopathy, and hypothermic therapy. Intrauterine hyperoxemia was defined as cord venous PO2 ≥ 90th percentile of the cohort. Adjusted relative risks (aRR) were estimated for neonatal morbidity controlling for confounders. Analysis was performed for the entire cohort and stratified by the presence of acidemia defined as umbilical artery pH<7.1. Results Of 7,789 patients with validated paired cord gases, 106 (1.4%) had the composite neonatal morbidity. There was no difference in composite neonatal morbidity in patients with and without intrauterine hyperoxemia in the entire cohort (1.5% vs 1.3%, aRR 1.5, 95% CI 0.9–2.7). The rate of acidemia was not significantly different in the two groups (1.9% vs 1.8%, aRR 1.5, 95% CI 0.9–2.5). In stratified analysis, there was evidence of effect modification (p for interaction <0.001), with a significant association between intrauterine hyperoxemia and neonatal morbidity in the presence of acidemia (41.2% vs 21.4%, aRR 2.3, 95% CI 1.1–3.5), but not in its absence (0.8% vs 1.0%, aRR 1.0, 95% CI 0.5–2.2). Conclusion Intrauterine hyperoxemia, compared with normoxemia, is associated with a small, but significantly increased risk of neonatal morbidity in acidemic neonates.

Maternal oxygen in labor: False reassurance?

“…Composite morbidity (mechanical ventilation, hypothermic therapy, meconium aspiration, and death) was significantly increased in neonates with both hyperoxia and acidemia compared with nonacidemic hyperoxic infants. 9 This is further supported by reports of an increased need for neonatal resuscitation and a fourfold increase in umbilical cord pH of less than 7.2. 10 While intrauterine and extrauterine life certainly differ, these findings align with the pediatric literature that supports neonatal resuscitation with room air rather than 100% oxygen.…”

“…This is exactly what Raghuraman and colleagues demonstrated in a large prospective cohort analysis. 9 While there was no difference in neonatal morbidity between those receiving oxygen and those on room air, there was a significant difference among infants with acidemia and hyperoxia. Composite morbidity (mechanical ventilation, hypothermic therapy, meconium aspiration, and death) was significantly increased in neonates with both hyperoxia and acidemia compared with nonacidemic hyperoxic infants.…”

Umbilical Cord Oxygen Content and Neonatal Morbidity at Term

“…Samples were considered paired if the cord pH was at least 0.02 lower in the artery than the vein. 6,14,15 Data regarding maternal demographics, antenatal course, intrapartum events, and neonatal diagnoses were extracted from medical records by trained research staff. The primary outcome in assessing the predictive ability of umbilical cord oxygen content was a composite of neonatal morbidity that included intubation, mechanical ventilation, meconium aspiration syndrome, hypoxic-ischemic encephalopathy, need for hypothermia treatment, and neonatal death.…”

“…The primary outcome in assessing the predictive ability of umbilical cord oxygen content was a composite of neonatal morbidity that included intubation, mechanical ventilation, meconium aspiration syndrome, hypoxic-ischemic encephalopathy, need for hypothermia treatment, and neonatal death. 6,14,16 Only one diagnosis was counted per patient. The diagnosis of meconium aspiration syndrome was made by neonatal respiratory distress in the setting of meconium stained amniotic fluid and associated radiographic abnormalities.…”

Differences between umbilical blood gas in term and preterm newborns

“…Therefore, for early and accurate detection of the health status of newborns, a complete approach would include both the UA and UV sampling. Studies on differences between UA and UV pH showed that pH, measured in the UA can give valuable information and is useful in predicting the neonatal outcome in term infants (8,9). There is a lack of evidence reporting differences between UA and UV in preterm newborns.…”