1067 Electronic FHR monitoring, pH and newborn outcomes – this is as good as it gets

Abstract

To examine the relationship between umbilical artery (UA) cord gas values and fetal tolerance of labor and/or delivery. We hypothesized the existence of wide biologic variability in fetal tolerance of metabolic acidemia which, if present, would weaken a fundamental assumption underlying the use of EFHRM. A retrospective cohort study of term, singleton fetuses delivered between 2012 and 2020. Universal cord gases were collected. Umbilical cord gas values and Apgar scores were extracted. We calculated Spearman correlation coefficients (CC) and constructed ROC curves for UA pH and base excess (BE) as predictors of Apgar score. Our cohort included cord gas and Apgar scores from 29,787 deliveries. The statistical correlation between UA pH and BE and both 1 and 5 minute Apgar scores was weak or non-existent in both the group as a whole and in all pH range sub-groups (Table 1). ROC curve analysis of pH as a predictor of 5 minute Apgar >=7 showed only an acceptable discrimination (AUC= 0.75 95%CI 0.71-0.79, p< 0.01)) with a similar story for base excess (AUC=0.745 95%CI 0.708-0.782, p< 0.01). Subgroup analysis of deliveries with pH >7.2 or BE >-4 showed even poorer predictive ability (Figure 1). Of 8 newborns who underwent cooling for HIE, 3 (38%) had UA pH > 7.15. The use of EFHRM is predicated upon a documented correlation between certain FHR patterns and UA pH, and an arbitrary, presumed correlation between pH and fetal tolerance of labor/delivery, as reflected in newborn condition. To the extent that the latter relationship is invalid, the former correlation is irrelevant. Our data demonstrate a weak to absent correlation between metabolic acidemia and even short term fetal condition, confirming wide biologic variability in fetal tolerance of the hypoxic stress of labor and significantly weakening this latter assumption. No amount of future tweaking of FHR pattern interpretation is likely to result in improved newborn outcomes given this flaw in one fundamental assumption upon which FHRM is based.View Large Image Figure ViewerDownload Hi-res image Download (PPT)