Dear Editor:
I read with interest the article of Holcroft et al.1 in which they conclude that there is no deterioration in fetal cord gas results after 30 minutes from decision to delivery for “urgent” or “emergent” cesarean sections. Although I appreciate the reference to our manuscript2 for the assessment of potential changes in base excess over time, I question the major conclusion of the manuscript that “in neither the emergent nor urgent group did umbilical arterial gas results deteriorate after 30 minutes.” The authors report linear regressions of the changes in umbilical artery pH and base excess versus decision to delivery intervals. These regressions demonstrated a paradoxical, marginally improved base excess with longer decision to delivery intervals among both the emergent and urgent groups. They suggest that for most fetuses delivered emergently for nonreassuring fetal status, there is no evidence that they are indeed developing metabolic acidosis. Yet the mean umbilical arterial base excess was −8.8 in the patients delivered emergently, a value significantly more acidotic than that of the patients delivered urgently. I believe the authors misinterpret the essentially flat regression line as suggesting that the individual fetus does not develop further metabolic acidosis from decision to delivery. The linear regression results from an uncontrolled cross-sectional population cannot be utilized to suggest that individual fetal arterial base excess values do not change during the period of decision to delivery. Although the posthoc maternal–fetal medicine reviewers judged the tracings as either “emergent” versus “urgent”, the actual time from decision to delivery likely reflected the perceived urgency of delivery of the responsible clinicians. Thus, for example, patients with acute severe bradycardia may have undergone a “crash” cesarean section while those with less concerning fetal heart tracings, though still posthoc classified as “emergent”, may have had a less emergent delivery. This type of clinical triaging may explain the linear regression results.
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