The following is a summary of “A comparison of criteria for defining metabolic acidemia in live-born neonates and its effect on predicting serious adverse neonatal outcomes,” published in the OCTOBER 2023 issue of Obstetrics and Gynecology by Kraus, et al.

Metabolic acidemia poses a recognized risk for severe adverse outcomes in neonates, impacting both preterm and term infants. For a study, researchers sought to assess the clinical relevance of umbilical cord gas measurements at delivery concerning serious adverse neonatal outcomes. Additionally, they aimed to investigate whether distinct thresholds for defining metabolic acidemia vary in their predictive capacity for adverse neonatal complications.

Conducted as a retrospective cohort study, the research encompassed singleton live-born deliveries occurring between January 2011 and December 2019. Stratification based on gestational age at birth (≥35 and <35 weeks of gestation) was executed, enabling comparisons of maternal characteristics, obstetrical complications, intrapartum events, and adverse neonatal outcomes between neonates with and without metabolic acidemia. The definition of metabolic acidemia, as determined by umbilical cord gas analyses, adhered to criteria from both the American College of Obstetricians and Gynecologists and the Eunice Kennedy Shriver National Institute of Child Health and Human Development. The primary outcome of interest was hypoxic-ischemic encephalopathy requiring whole-body hypothermia.

A total of 91,694 neonates born at ≥35 weeks of gestation were included in the study. According to the American College of Obstetricians and Gynecologists criteria, 2,659 (2.9%) infants had metabolic acidemia. Neonates with metabolic acidemia faced significantly elevated risks for neonatal intensive care unit admission, seizures, respiratory support necessity, sepsis, and neonatal death. Notably, metabolic acidemia, as per American College of Obstetricians and Gynecologists criteria, was associated with an almost 100-fold increased risk of hypoxic-ischemic encephalopathy requiring whole-body hypothermia (relative risk, 92.69; 95% confidence interval, 64.42–133.35) in neonates born at ≥35 weeks of gestation. Several maternal factors, including diabetes mellitus, hypertensive disorders of pregnancy, post-term deliveries, prolonged second stages, chorioamnionitis, operative vaginal deliveries, placental abruption, and cesarean deliveries, were linked with metabolic acidemia in neonates born ≥35 weeks of gestation. The highest relative risk was observed in those diagnosed with placental abruption (relative risk, 9.07; 95% confidence interval, 7.25–11.36). Similar findings were observed in the neonatal cohort born <35 weeks of gestation. When comparing neonates born ≥35 weeks of gestation with metabolic acidemia by American College of Obstetricians and Gynecologists criteria vs. Eunice Kennedy Shriver National Institute of Child Health and Human Development criteria, the latter identified more neonates at risk for serious adverse neonatal outcomes. Specifically, 4.9% more neonates were diagnosed with metabolic acidemia, and 16 more term neonates were identified as requiring whole-body hypothermia. Mean 1-minute and 5-minute Apgar scores were similar and reassuring among neonates born at ≥35 weeks of gestation with and without metabolic acidemia, as defined by both the American College of Obstetricians and Gynecologists and Eunice Kennedy Shriver National Institute of Child Health and Human Development criteria (8 vs. 8 and 9 vs. 9, respectively; P<.001). Sensitivity and specificity were 86.7% and 92.2%, respectively, with the Eunice Kennedy Shriver National Institute of Child Health and Human Development criteria and 74.2% and 97.2% with the American College of Obstetricians and Gynecologists criteria.

Infants with metabolic acidemia identified through cord gas collection at delivery face a significantly elevated risk of serious adverse neonatal outcomes. Notably, they exhibit an almost 100-fold increased risk of hypoxic-ischemic encephalopathy requiring whole-body hypothermia. The use of the more sensitive Eunice Kennedy Shriver National Institute of Child Health and Human Development criteria for defining metabolic acidemia proved to be valuable in identifying more neonates born at ≥35 weeks of gestation who are at risk for adverse neonatal outcomes, including hypoxic-ischemic encephalopathy requiring whole-body hypothermia. It emphasized the importance of accurate and sensitive criteria in identifying infants at risk and ensuring timely interventions for improved outcomes.

Source: ajog.org/article/S0002-9378(23)00194-1/fulltext