Objective: The aim of this study was to identify fetal heart rate abnormalities (FHRA) in the two hours preceding uterine rupture during trial of labor after a previous C-section compared with successful vaginal birth after cesarean controls.
Study design: A multicenter case-control study was conducted from 2006 to 2012. Fetal heart rate tracings of the two-hour period preceding delivery were segmented, anonymized and independently classified by two obstetricians according to a standardized grid based on FIGO guidelines (4 grades: 1 - normal, 2 - intermediate, 3 - abnormal, 4 - preterminal). Each case of uterine rupture was matched to 2 controls. Survival curves were generated for both groups using the Kaplan-Meier method to analyze the occurrence of each FHR category across time.
Results: During the study period, 39,773 patients gave birth. 2649 involved women with a previous C-section (6.6%). A total of 33 uterine rupture/scar dehiscence cases occurred (0.08% of all births), of which 22 were included. These were matched to 44 controls. FIGO grade-3 FHRA were significantly associated with uterine rupture in the hour preceding its diagnosis: odds ratios were 4.1 (95% CI 1.2-14.0), 4.3 (95% CI 1.4-13.0) and 3.7 (95% CI 1.2-11.3), in the 60-40 min, 40-20 min and last 20 min before childbirth, respectively. Agreement between the two reviewers (Cohen's kappa) was 84% (CI 95%: 0.79-0.89).
Conclusion: In the hour preceding uterine rupture, there are often significant FHRA. This leads us to consider the possibility of an earlier C-section when faced with grade-3 FHRA, before the onset of terminal bradycardia jeopardizing maternal and fetal prognosis.
Keywords: Fetal heart rate; Risk management; Trial of labor after C-section (TOLAC); Uterine rupture.
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