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Canada's cesarean delivery (CD) rate continues to increase. The Society of Obstetricians and Gynaecologists of Canada advocates the use of the modified Robson classification for comparisons. This study describes national and provincial CD rates according to this classification system.
All 2016-2017 in-hospital births in Canada (outside Québec) reported to the Discharge Abstract Database were categorized using the modified Robson classification system. CD rates, group size, and contributions of each group to the overall volume of CD were reported. Rates by province and hospital peer group were also examined (Canadian Task Force Classification III).
A total of 286 201 women gave birth; among these, 83 262 (29.1%) had CDs. Robson group 5 (term singleton previous CD) had a CD rate of 80.5% and was the largest contributing group to the overall number of CD (36.6%). Women whose labour was induced (Robson group 2A) had a CD rate almost double the rate of women with spontaneous labour (Robson group 1): 33.5% versus 18.4%. These latter two groups made the next largest contributions to overall CD (15.7% and 14.1%, respectively). There were substantial variations in CD rates across provinces and among hospital peer groups.
The study found large variations in CD rates across provinces and hospitals within each Robson group, thus suggesting that examining variations to determine the groups contributing the most to CD rates (Robson groups 5, 2A, and 1) may provide valuable insight for reducing CD rates. This study provides a benchmark for measuring the impact of future initiatives to reduce CD rates in Canada.
Le taux de césariennes au Canada continue d'augmenter. La Société des obstétriciens et gynécologues du Canada prône le recours à la classification de Robson modifiée pour comparer les taux. Cette étude décrit les taux de césariennes du pays et des provinces d'après ce système de classification.
Toutes les naissances en milieu hospitalier déclarées de 2016 à 2017 au Canada (excluant le Québec) dans la Base de données sur les congés des patients ont été classées d'après le système de classification de Robson modifié. Les données compilées comprennent le taux de césariennes, la taille du groupe et la contribution de chaque groupe au volume total de césariennes pratiquées. Les taux par province et par groupe d'hôpitaux semblables ont aussi été étudiés (classification III du Groupe d'étude canadien sur les soins de santé préventifs).
Un total de 286 201 femmes ont accouché, dont 83 262 (29,1 %) par césarienne. Le groupe Robson 5 (grossesse monofœtale à terme avec antécédent de césarienne) a obtenu un taux de césariennes de 80,5 %, soit la plus forte contribution au taux global de césariennes (36,6 %). Le taux de césariennes des femmes ayant subi un déclenchement artificiel (groupe Robson 2A) était presque le double de celui des femmes dont le travail s'était déclenché spontanément (groupe Robson 1) : 33,5 % par rapport à 18,4 %. Ces deux derniers groupes ont apporté les 2e et 3e plus fortes contributions au taux global de césariennes (15,7 % et 14,1 %, respectivement). Des variations importantes ont été observées dans les taux de césariennes entre les provinces et entre les groupes d'hôpitaux semblables.
L'étude fait état de grandes variations dans les taux de césariennes entre les provinces et les hôpitaux au sein de chaque groupe Robson, ce qui laisse entendre que l'examen des variations pour déterminer les groupes qui contribuent le plus au taux de césariennes (groupes Robson 5, 2A et 1) pourrait fournir une perspective pertinente pour réduire ce taux. Cette étude fournit un point de comparaison qui permet de mesurer les retombées des prochaines mesures visant à réduire le taux de césariennes au Canada.
representing a 50.8% increase in the past 20 years. This is similar to what is seen globally, with rates in many countries increasing by about 40% between 2000 and 2015. The observed increases in CD rates can be attributed to women giving first birth at a later age, increases in maternal obesity, use of fertility treatments, convenience for both physicians and patients, and more women being inclined to have a CD.
Understanding CD rates is challenging because many factors contribute to the overall rate. In 2001, Robson published a 10-group classification system to describe CDs within mutually exclusive groups of women with particular obstetric characteristics as a first step in addressing concerns about rising rates.
The Robson Classification uses clinical factors, such as parity, previous CD, gestational age, onset of labour, fetal presentation, and number of fetuses to categorize obstetric populations into relatively homogenous patient groups. In 2012, the Society of Obstetricians and Gynaecologists of Canada (SOGC) modified the 2001 Robson classification by adding subcategories for women having CDs after spontaneous onset of labour, after induction of labour, and before labour (Table 1). Furthermore, the SOGC endorsed the use of the modified Robson classification to compare CD rates across Canada.
The modified Robson classification allows examination of group-specific rates to ascertain the suitability of the rate. In addition, it shows how the relative size of each group and the magnitude of group-specific rates affect the overall CD rate, consequently identifying groups that contribute the most to the overall CD rate.
Table 1Maternal characteristics by the modified Robson classification in Canada (excluding Québec), 2016-2017
Morbid obesity as identified by a physician on a patient chart and captured by International Statistical Classification of Diseases and Related Health Problems, 10th Revision, Canada, codes of E66.2, E66.8, or O99.201.
1. Nullipara, singleton cephalic, ≥37 weeks, spontaneous labour
2. Nullipara, singleton cephalic, ≥37 weeks
B: CD before labour
3. Multipara, singleton cephalic, ≥37 weeks, spontaneous labour with no previous CD
4. Multipara, singleton cephalic, ≥37 weeks with no previous CD
B: CD before labour
5. Previous CD, singleton cephalic, ≥37 weeks
6. All nulliparous breeches
7. All multiparous breeches (including previous CD)
8. All multiple pregnancies (including previous CD)
9. All abnormal lies (including previous CD but excluding breech)
10. All singleton cephalic, ≤36 weeks (including previous CD)
Total obstetric population
CD: cesarean delivery.
a Includes pre-pregnancy and gestational diabetes.
b Includes pre-pregnancy and gestational hypertension, preeclampsia and eclampsia.
c Morbid obesity as identified by a physician on a patient chart and captured by International Statistical Classification of Diseases and Related Health Problems, 10th Revision, Canada, codes of E66.2, E66.8, or O99.201.
To date, however, no pan-Canadian research has been conducted.
The aim of this study was to examine CD rates across Canada by using the modified Robson classification system at national, provincial, and hospital peer group levels and to identify groups that contribute most to the overall number of CDs. Identifying such groups will help in devising ways to reduce CD rates in Canada.
We conducted a retrospective analysis of all in-hospital deliveries in Canada (excluding Québec), by using the Discharge Abstract Database. This data holding, managed by the Canadian Institute for Health Information (CIHI), captures administrative, clinical, and demographic information on all patients discharged from acute care hospitals in Canada outside Québec. Québec data were not included in the analysis because parity information is currently not available in the province's clinical administrative data submitted to CIHI. The enhanced Canadian version of the International Statistical Classification of Diseases and Related Health Problems, 10th Revision, Canada (ICD-10-CA) and the Canadian Classification of Health Interventions were used to capture diagnoses and procedures during hospital stays.
In the analysis, we included all women who had given birth in an acute care hospital and were discharged between April 1, 2016, and March 31, 2017. Home births, stillbirths, and terminations of pregnancy were excluded from the analysis. Relevant information, such as previous births (nulliparous or multiparous), number of fetuses (single or multiple), gestational age at the time of delivery, fetal presentation (cephalic, breech, or transverse), and onset of labour and delivery (spontaneous, induced, or planned CD), was directly obtained from the relevant data elements or identified by ICD-10-CA and/or Canadian Classification of Health Interventions in the Discharge Abstract Database. Births were categorized into the modified Robson 10-group clinical criteria endorsed by the SOGC.
For each Robson group, we described maternal characteristics, medical conditions, and obstetric conditions (Table 1), and we reported the number of CDs, number of deliveries, CD rate, proportion of deliveries, and proportion of overall CDs at the national level (Table 2). At the provincial level, we reported CD rates and proportion of deliveries. We did not report results for the three territories because of small numbers. However, their counts are included in the overall results. Rates were calculated by dividing the number of CDs by the number of deliveries and were expressed as a percentage. At hospital peer-group levels, we reported CD rates and 95% and 99.8% confidence limits using funnel plots. The funnel plots show CD rates against the denominator for that rate (i.e., number of obstetric cases) for each hospital, displayed as a scatter plot. The solid horizontal line in the middle of the funnel represents the national CD rate of each Robson group. The outside funnel represents the national 99.8% confidence limits (3 SDs from the average); the inner funnel represents the national 95% confidence limits (2 SDs from the average). The Hospital Peer Group methodology was developed by CIHI.
Research ethics board review was not required by the Government of Canada Panel on Research Ethics because the research involved secondary use of routinely collected clinical administrative health information and was not re-identifiable. Data analysis was performed with SAS Enterprise Guide software version 7.1 (SAS Institute, Inc., Cary, NC).
The total number of women who gave birth in Canadian hospitals outside Québec was 286 201 in 2016-2017. All but 333 (0.1%) of the deliveries could be categorized into the 10 Robson categories. Maternal characteristics, medical conditions, and obstetric conditions are shown in Table 1. Among 286 201 births, 83 262 were CD, for a rate of 29.1%.
The largest contributing group to the overall number of CDs consisted of women with a term singleton cephalic-presenting pregnancy who had at least one previous CD (Robson group 5). Although this group accounted for only 13.2% of the total obstetric population, it had a CD rate of 80.5% and the largest absolute number of CDs (30 437 of 83 262) (Table 2).
Nulliparous women with a term singleton cephalic-presenting pregnancy with induced labour (Robson group 2A) made the second-largest contribution to the overall number of CDs. This group accounted for 13.7% of the total obstetric population, with a CD rate of 33.5%.
Nulliparous women with a term singleton cephalic-presenting pregnancy who had spontaneous labour (Robson group 1) made the third-largest contribution to the overall volume of CDs. This group accounted for almost one fourth of the total obstetric population (22.3%). The CD rate in this group was 18.4%.
The largest group in the overall obstetric population was Robson group 3 (multiparous women with a term singleton cephalic-presenting pregnancy and spontaneous labour with no previous CD). However, this group had a low CD rate at 2.9% and did not contribute significantly to the overall number of CDs.
Analyses by province are presented in Table 3. Similar to the results at the national level, Robson group 5 made the largest contribution to the number of CDs across all provinces, followed by group 2A and group 1, except in British Columbia, where groups 2A and 1 were reversed in order of contribution. However, group-specific CD rates varied by province. For example, for Robson group 1, CD rates ranged from 14.4% in Saskatchewan to 25.1% in British Columbia. For Robson group 2, the CD rates ranged from 31.2% in Manitoba to 51.2% in British Columbia.
Table 3Proportion and cesarean delivery (CD) rate of each Robson group by province in Canada (excluding Québec), 2016-2017
Analysis by hospital peer group revealed that among 286 201 births in 2016-2017, 43.0% were delivered in teaching hospitals, 40.7% in large community hospitals, 12.3% in medium community hospitals, and 4.1% in small community hospitals. There was substantial variation in CD rates among hospital peer groups. A set of funnel plots showing hospital variation by hospital peer group for the largest Robson groups is presented in the Figure. The CD rates in almost all medium and small community hospitals were within 3 SDs (99.8%) of the national mean. However, several teaching and large community hospitals had CD rates greater than 3 SDs above the mean (Robson groups 1, 2A, 3, 4A, and 10). For Robson group 5, some teaching hospitals had CD rates more than 3 SDs below the mean (Figure).
This study examined all in-hospital births in Canada outside Québec and classified them using the modified Robson criteria to describe obstetric practice patterns. To our knowledge, this is the first pan-Canadian study to use the Robson classification to assess CD rates on the basis of a national data source.
In 2016-2017, the Canadian CD rate was 29.1% (excluding Québec), higher than the Organisation for Economic Co-operation and Development average of 27.9%.
Examining CD rates using the modified Robson classification provides a starting point for understanding the variations. In countries such as the Netherlands, Iceland, and Norway, CD rates are substantially lower across all Robson groups, especially groups 1, 3, and 5.
Understanding the reasons for these differences can shed light on potential strategies to reduce CD rates in Canada. In the Netherlands, for example, 71% of women in Robson group 5 had a trial of labour, and 75% of these women had a successful vaginal birth, thus resulting in a low CD rate of 47.1% for this group.
studies have shown that when candidates are selected carefully, a trial of labour is a safe choice, with risks of adverse perinatal outcomes for vaginal birth after previous CD similar to those in nulliparous mothers with singleton cephalic presentation.
Given that this group is the largest contributor to the overall number of CD in Canada (with rates almost double that of the Dutch), targeting this group is likely to have the greatest impact on CD rates in Canada. According to recent SOGC clinical guidelines, women with previous CD who have no contraindications should consider a trial of labour within hospitals that can provide close monitoring and a timely CD if required.
Reducing CD rates among nulliparous women (e.g., Robson groups 1 and 2A) would also be effective in reducing overall rates. This may be achieved through quality improvement strategies, such as those used in a cluster randomized controlled trial (RCT) wherein interventions focused on review of CD indications, feedback for health professionals, and application of best practices. This study demonstrated a significant reduction in the CD rate without adverse effects on maternal or neonatal outcomes.
Additionally, current evidence suggests that diagnostic criteria for labour dystocia and arrest, the most frequent diagnoses (34%) in women undergoing a primary CD, are too stringent and that a continued trial of labour can be safely attempted in the majority of these cases.
Given that CD rates for Robson group 2A are almost twice those of Robson group 1, targeting labour induction practices may be another way to reduce CD rates among nulliparous women. A recent RCT showed that low-risk nulliparous women undergoing an elective induction of labour at 39 weeks had a CD rate of 18.6%, which is similar to that in women in spontaneous labour.
This finding suggests that increased CD rates may be related to the indication for induction of labour rather than the induction itself. Nonetheless, findings from the literature suggest that clinical decision making for induction of labour varies among health professionals.
Quality improvement programs such as improving labour induction guidelines, selecting the appropriate induction method, and clarifying the definition of failed induction have been effective in reducing the number of elective inductions and unplanned CDs.
Yet our study found large variations in CD rates within the Robson groups among both provinces and hospitals. We took a closer look at Robson group 1 and further excluded women with pre-existing risk factors to create a very homogenous low-risk group and still found provincial-level and hospital-level variations, even among this very low-risk group (results not shown). These findings suggest differences in clinical practices.
In our study, more than 80% of deliveries occurred in teaching and large community hospitals. These hospitals contributed to about 85% of the overall volume of CD with rates in teaching hospitals being the highest. Although we expect rates to be higher among teaching hospitals given their treatment of higher-risk pregnancies, the large interhospital variation found within the Robson groups suggests that focusing on teaching and large community hospitals to find the causes of variation is likely to have the greatest impact on CD rates.
This study has several strengths. We used routinely collected data from across Canada, and this allowed for the first comprehensive national assessment of CD rates using the Robson classification. Additionally, an internationally recognized classification system was used, allowing more meaningful comparisons with other countries.
This study also has limitations. First, for the purposes of hospital comparisons, we used CIHI hospital peer groups rather than obstetric level of care classifications
because the latter are not available consistently for all hospitals in Canada. The CIHI hospital peer-group methodology groups together facilities that have similar structural and patient characteristics overall, but differences in obstetric populations may exist. Second, this is a retrospective study; therefore, unlike an RCT, definitive conclusions regarding Robson group comparisons cannot be made. Finally, the study analyzed CD rates and did not examine patient outcomes or experiences, such as maternal and neonatal morbidity and mortality, neonatal intensive care unit admissions, or patient satisfaction. Therefore, we cannot comment on whether higher CD rates are associated with any of these parameters.
In our study, we found that women giving birth after a prior CD had the largest impact on Canada's CD rate, and women whose labour was induced had a higher CD rate compared with women who had spontaneous labour. Additionally, there were variations in CD rates among provinces and hospitals within each Robson group. These findings will help to identify strategies for reducing CD rates in Canada, with specific focus on the groups with the greatest impact and on reducing the variations within these groups.
Guerrero Vela M
Searching for the optimal rate of medically necessary cesarean delivery.