Fetal heart rate abnormalities associated with uterine rupture: a case–control study: A new time-lapse approach using a standardized classification

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Abstract

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.

Introduction

The increasing rate of cesarean delivery confronts obstetricians with the need to manage a growing number of patients with uterine scarring.

In 2010, the reported Cesarean section rate was 25.2% in northern European countries [1] and 32.9% in the U.S. [2].

Many different health authorities approve of, even encourage, vaginal birth after cesarean delivery (VBAC) under certain conditions [3], [4], [5], [6], [7].

While VBAC diminishes maternal and perinatal morbidity associated with iterative C-section deliveries, it does expose to the risk of uterine rupture (UR), estimated to occur in 0.5% of cases (95% confidence interval, 0.306–0.685%) [8].

The lack of specific clinical warning signs for UR explains why diagnosis is often delayed, exposing to life-threatening maternal and fetal compromise [8], [9], [10], [11], [12], [13].

It has been reported that fetal heart rate abnormalities (FHRA) consisting of variable or late decelerations occur prior to UR in 55–87% of cases [9], [10], [14], [15], [16], [17], [18], [19]. A case–control study found that terminal bradycardia was significantly associated with UR in patients with a previous C-section [14].

This severity of bradycardia is associated with poor perinatal outcome, despite the urgent delivery that takes place.

Finding FHRA associated with UR other than bradycardia and of earlier onset could help minimize maternal and neonatal morbi-mortality.

The aim of this study was to characterize fetal heart rate patterns in the two hours preceding uterine rupture compared with successful vaginal birth after cesarean (VBAC) controls.

Assessing elapsed time between the onset of grade 3 FHRA (FIGO classification) and diagnosis of uterine rupture was its secondary aim.

Section snippets

Material and methods

A multicenter case–control study was conducted between January 1, 2006 and July 31, 2012 in four maternity wards of the Poitou-Charentes region of France.

Data collection

Obstetric records of patients from each maternity ward were reviewed for cases of uterine rupture, as defined by the International Classification of Diseases (ICD-10).

Patients had to meet the following inclusion criteria:

  • Women with at least one previous C-section;

  • Complete UR according to Plauché [20] or uterine scar dehiscence during labor (defined by rupture of the entire uterine wall with an intact serosa), confirmed operatively;

  • Singleton pregnancy, cephalic presentation, gestational age

Data analysis

In the case group, fetal heart rate tracings of the two-hour period preceding diagnosis of uterine rupture were examined. In the control group, heart rate tracings of the two-hour period prior to the onset of expulsive efforts or C-section were analyzed.

The strips were divided into 20-min segments, anonymized and randomly ordered.

The selected segments were independently evaluated by two senior grade obstetricians and classified according into four grades of increasing severity: normal,

Results

Thirty-nine thousand seven hundred and seventy-three women delivered in one of the four centers during the study period, out of which 2649 (6.6%) had a previous C-section. Out of these, 1841 (70%) underwent trial of labor and 1372 (74%) had a successful vaginal birth (Fig. 2).

A total of 33 uterine rupture/scar dehiscence cases occurred (18 full ruptures), representing 0.08% (33/39773) of all births, 1.2% (33/2649) of births after a previous C-section and 1.5% (27/1841) of TOLACs.

Concerning the

Data analysis

There were no statistically significant differences between cases and controls for the analyzed characteristics (Table 1).

Out of the potential 396 FHR tracing segments (66 patients × 6), 359 were obtained. For 5 patients, the time lapse between admission in the delivery unit and birth was less than two hours.

Agreement between the two reviewers for the four FHR categories was very good, with a Cohen's kappa value of 84% (CI 95%: 0.79–0.89).

In the rare cases of a disagreement between the two

Discussion

Our study shows that, in the 60–40 min preceding childbirth, the onset of grade 3 FHRA is significantly associated with UR during TOLAC.

Since no systematic uterine revision was carried out following VBAC, it is possible that this study underestimated the number of uterine rupture/scar dehiscence cases. However, such a classification bias is rather unlikely given the strong link between UR and FHRA.

Intra- and inter-observer variability in interpretation of FHR [25] may also be a debatable point

Conclusion

This study found a significant association between grade-3 FHRA during TOLAC and uterine rupture, in the hour preceding its diagnosis.

Given these results, from a risk management standpoint, in the event of grade-3 FHRA during TOLAC, immediate C-section without resort to a second line method of fetal monitoring would constitute a reasonable therapeutic option.

Detection of early-onset FHRA during TOLAC could help identify patients at risk of UR, thus warning clinicians and possibly preventing

Ethics statement

In France, the 2004 Bioethics Law authorizes physicians to carry out retrospective studies without obtaining participants’ explicit consent as long as confidentiality is strictly maintained. This study's anonymization process was submitted to the CNIL (French Data Protection Authority) and validated.

Author contributions

Dr. Desseauve takes responsibility for the integrity of the data and the accuracy of the data analysis. D.D. jointly conceived the study with F.P. M.B.-G and J.L. collected data. M.B.-G., J.L. and F.P. interpreted fetal heart rate patterns. D.D. and X.F. performed statistical analysis. D.D., F.P., M.B.-G. and X.F. interpreted the data and wrote the manuscript.

Funding

The authors received no financial support for this study.

Conflict of interest

The authors have no relevant financial or commercial interest in this article.

Acknowledgements

We would like to thank Pascal Villemonteix (MD, Bressuire), Denis Tariel (MD, Angoulême) and Alain Godard (MD, Châtellerault) who lent us their support in gathering cases of uterine rupture.

We likewise wish to thank Caroline Rutten, a medical student at the University of Poitiers, for translating and editing the original manuscript.

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