Objective: To estimate whether fetal bradycardia-to-delivery interval or decision-to-delivery interval was related to cord arterial pH according to different causes of fetal distress.
Methods: Women who delivered singleton neonates by urgent cesarean delivery because of intrapartum fetal bradycardia were retrospectively categorized into three groups according to the cause of fetal bradycardia: 1) Irreversible; 2) Potentially Reversible; and 3) Unknown (no identifiable cause). Comparisons were made between groups in regard to pH, bradycardia-to-delivery interval, and decision-to-delivery interval. Correlation analyses between pH and both intervals were then performed for different groups.
Results: Of 235 cases, 39, 22, and 174 were respectively categorized into the Irreversible group, Potentially Reversible group, and Unknown group. The median pH was lower in the Irreversible group (7.094; interquartile range [IQR] 6.991-7.216) than in Potentially Reversible group (7.162; IQR 7.064-7.251) or Unknown group (7.210; IQR 7.161-7.255) (P<.001). The Irreversible group's median bradycardia-to-delivery interval was 5 minutes shorter than those of the other two groups (11 compared with 16.5 and 16 minutes, respectively; P<.001), whereas its median decision-to-delivery interval was 1 minute shorter (10 compared with 11.5 and 11 minutes, respectively; P=.001). In the Irreversible group, pH decreased with the bradycardia-to-delivery interval (Spearman's rho=-0.354; P=.027) at a rate of 0.011 per minute. Cord arterial pH did not correlate with the bradycardia-to-delivery interval in the Potentially Reversible and Unknown groups. In neither group did pH correlate with decision-to-delivery interval.
Conclusion: Cord arterial pH deteriorates with bradycardia-to-delivery interval when the underlying cause of fetal distress is irreversible, but not so otherwise.
Level of evidence: II.