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Department of Pediatrics, McGill University, Montréal, QCDepartment of Epidemiology, Biostatistics, and Occupational Heath, McGill University, Montréal, QC
This study sought to quantify temporal trends and provincial and territorial variations in severe maternal morbidity (SMM) in Canada.
Methods
The study used data on all hospital deliveries in Canada (excluding Québec) from 2003 to 2016 to examine temporal trends and from 2012 to 2016 to study regional variations. SMM was identified using diagnosis and intervention codes. Contrasts among periods and regions were quantified using rate ratios (RRs) and 95% confidence intervals (CIs). Temporal changes were also assessed using chi-square tests for trend (Canadian Task Force Classification II-1).
Results
The study population included 3 882 790 deliveries between 2003 and 2016 and 1 418 545 deliveries between 2012 and 2016. Severe hemorrhage rates increased from 44.8 in 2003 to 62.4 per 10 000 deliveries in 2012 (P for trend <0.0001) and then declined to 41.8 per 10 000 deliveries in 2016 (P for trend <0.0001). Maternal intensive care unit admission and sepsis rates decreased between 2003 and 2016, whereas rates of stroke, severe uterine rupture, hysterectomy, obstetric embolism, shock, and assisted ventilation increased. Rates of composite SMM in 2012-2016 were higher in Newfoundland and Labrador (RR 1.15; 95% CI 1.04–1.26), Nova Scotia (RR 1.11; 95% CI 1.03–1.19), New Brunswick (RR1.22; 95% CI 1.13–1.32), Manitoba (RR 1.09; 95% CI 1.03–1.15), Saskatchewan (RR 1.15; 95% CI 1.09–1.22), the Yukon (RR 1.74; 95% CI 1.35–2.25), and Nunavut (RR 1.76; 95% CI 1.46–2.11) compared with the rest of Canada, whereas rates were lower in Alberta and British Columbia.
Conclusion
This surveillance report helps inform clinical practice and public health policy for improving maternal health in Canada.
Résumé
Objectif
Cette étude visait à quantifier les tendances temporelles et les différences entre les provinces et territoires en matière de morbidité maternelle grave (MMG) au Canada.
Méthodologie
L'étude s'est servie de données sur tous les accouchements ayant eu lieu à l'hôpital au Canada (à l'exception du Québec) : de 2003 à 2016 pour les tendances temporelles, et de 2012 à 2016 pour les différences régionales. Les cas de MMG ont été trouvés au moyen de leurs codes de diagnostic et d'intervention. Les différences entre les périodes et les régions ont été quantifiées à l'aide de ratios des taux (RT) et des intervalles de confiance (IC) à 95 %. Les changements temporels ont aussi été évalués avec le test de tendance du chi carré (classification II-1 du Groupe d'étude canadien).
Résultats
La population à l'étude totalisait 3 882 790 accouchements pour les années 2003 à 2016 et 1 418 545 accouchements pour les années 2012 à 2016. Le taux d'hémorragie grave par 10 000 accouchements est passé de 44,8 en 2003 à 62,4 en 2012 (P de tendance < 0,0001) puis est descendu à 41,8 en 2016 (P de tendance < 0,0001). Les taux d'admission de la mère aux soins intensifs et de septicémie ont diminué entre 2003 et 2016, alors que les taux d'accident vasculaire cérébral, de rupture utérine grave, d'hystérectomie, d'embolie obstétricale, de choc et de ventilation assistée ont augmenté. Les taux de MMG composite pour la période de 2012 à 2016 étaient plus élevés à Terre-Neuve-et-Labrador (RT : 1,15; IC à 95 % : 1,04-1,26), en Nouvelle-Écosse (RT : 1,11; IC à 95 % : 1,03-1,19), au Nouveau-Brunswick (RT : 1,22; IC à 95 % : 1,13-1,32), au Manitoba (RT : 1,09; IC à 95 % : 1,03-1,15), en Saskatchewan (RT : 1,15; IC à 95 % : 1,09-1,22), au Yukon (RT : 1,74; IC à 95 % : 1,35-2,25) et au Nunavut (RT : 1,76; IC à 95 % : 1,46-2,11) que dans le reste du Canada, et plus bas en Alberta et en Colombie-Britannique.
Conclusion
Ce rapport de surveillance permet de guider la pratique clinique et les politiques de santé publique dans l'amélioration de la santé maternelle au Canada.
Monitoring and surveillance of severe maternal morbidity (SMM) have received increasing emphasis in recent years, both because of the relative rarity of maternal deaths in high-income countries and because such morbidity has important short- and long-term consequences for maternal health. Temporal changes in maternal characteristics such as age and pre-pregnancy weight have also led to higher rates of pregnancy complications. For instance, the prevalence of pre-existing medical complications, such as chronic hypertension and diabetes mellitus, is substantially higher among women in their 30s and 40s,
Pre-pregnancy obesity, another increasingly prevalent maternal characteristic, is associated with higher rates of thromboembolism, pulmonary embolism, cerebrovascular morbidity, sepsis, acute renal failure, eclampsia, and maternal intensive care unit (ICU) admission.
Dayan N, Fell DB, Guo Y, et al. Severe maternal morbidity in women with high BMI in IVF and unassisted singleton pregnancies [e-pub ahead of print]. Hum Reprod doi: 10.1093/humrep/dey224, accessed March 27, 2019.
Population rates of SMM also reflect the quality of medical and obstetric care. Better identification, clinical monitoring, and management of high-risk women result in improved maternal outcomes. Paradoxically, improvements in medical care, especially for women with chronic disease (treatment of infertility is a notable example), have increased the proportion of high-risk pregnancies in recent years.
Dayan N, Fell DB, Guo Y, et al. Severe maternal morbidity in women with high BMI in IVF and unassisted singleton pregnancies [e-pub ahead of print]. Hum Reprod doi: 10.1093/humrep/dey224, accessed March 27, 2019.
Caesarean delivery, which has substantially reduced maternal morbidity and mortality from antepartum hemorrhage, obstructed labour, and other causes over the last several decades, has led to increased rates of adherent placenta in subsequent pregnancies.
Surveillance of SMM (i.e., assessment of temporal and regional variation in population rates of serious maternal illnesses) is important for the early identification of adverse changes in maternal health and for quantifying disparities in maternal health among subpopulations. The Canadian Perinatal Surveillance System began a program of extended maternal health surveillance in 2003 by moving beyond maternal mortality surveillance to assess population-based rates of SMM.
This report presents the most recent evaluation of SMM in Canada, according to a newly developed framework for identifying women with serious maternal conditions.
METHODS
We included all hospital deliveries in Canada from 2003 to 2016. Information on these deliveries was obtained from the Discharge Abstract Database of the Canadian Institute for Health Information. This database contained records for approximately 98% of all deliveries in Canada (excluding Québec), with information abstracted from medical records by trained personnel using standardized definitions and processes.
Details included maternal and infant characteristics, labour and delivery events, and diagnoses and procedures, with diagnoses coded using the International Statistical Classification of Diseases and Related Health Problems, 10th revision, Canadian version (ICD-10CA), and procedures coded using the Canadian Classification of Health Interventions (CCI). The validity of the information in the Discharge Abstract Database has been assessed against maternal and newborn medical records and shown to reflect the data in medical records accurately.
SMM was defined as a set of maternal conditions known to be associated with severe illness and characterized by prolonged hospitalization and high case fatality. Specific SMM subtypes were identified using a comprehensive list of maternal disease diagnoses (e.g., eclampsia), interventions (e.g., assisted ventilation), and conditions that signified organ failure (e.g., acute renal failure). This framework was developed by the Canadian Perinatal Surveillance System after evaluating candidate illnesses on the basis of a priori clinical considerations (related to illness severity), prolonged length of hospital stay, and high case fatality during the delivery admission (Dzakpasu S, Deb-Rinker P, Arbour L, et al. Severe maternal morbidity surveillance: monitoring pregnant women at high risk for prolonged hospitalization and death [submitted for publication]). It represents a formal revision of the previous 2010 definition of SMM
and was carried out to address various shortcomings, including the exclusion of severe preeclampsia and HELLP (hemolysis, elevated liver enzymes, low platelet count) syndrome cases as a result of coding limitations in the early version of ICD-10CA and the inclusion of conditions that did not necessarily represent SMM per se (e.g., asymptomatic human immunodeficiency virus infection).
The revised framework included 44 subtypes of SMM (online Appendix Table S1), identified using 76 ICD-10CA diagnosis codes (e.g., O14.1 for severe preeclampsia), 24 CCI intervention codes (e.g., 5.PC.91.HQ for surgical correction of inverted uterus), and three variables specifically collected by the Canadian Institute for Health Information (e.g., red cell transfusion). For ease of analysis and interpretation, we combined the 44 SMM subtypes into 13 broad SMM types: (1) severe preeclampsia, HELLP syndrome, and eclampsia; (2) severe hemorrhage; (3) maternal ICU admission; (4) surgical complications; (5) hysterectomy; (6) sepsis; (7) embolism, shock, and disseminated intravascular coagulation (DIC); (8) assisted ventilation; (9) cardiac conditions; (10) acute renal failure; (11) severe uterine rupture; (12) cerebrovascular accidents; and (13) miscellaneous SMM (online Appendix Table S1).
Analyses focused on composite SMM, SMM types, and SMM subtypes. SMM types and subtypes were not designed to be mutually exclusive. Thus, a woman requiring assisted ventilation who was admitted to the ICU would have been counted under both the assisted ventilation and ICU admission types of SMM, although she would have been included as a single case of SMM under composite SMM.
Temporal Trends and Regional Variations in Severe Maternal Morbidity
Temporal trends in specific SMM types and subtypes were assessed over the 14 years between 2003 and 2016. Because ICD-10CA codes for the identification of severe preeclampsia were not introduced until 2012, rates of this particular SMM (and therefore of composite SMM) were quantified only for the years 2012 to 2016. Temporal trends and regional differences in composite SMM, SMM types, and SMM subtypes were also assessed for the most recent 5-year period (2012-2016).
Analysis and Ethics Considerations
The frequency of composite SMM and of SMM types and subtypes was expressed using rates (per 1000 or per 10 000 deliveries) and their 95% confidence intervals (CIs). Rate ratios and 95% CIs were used to contrast rates in different years and between each province or territory and the rest of Canada (excluding Québec). Chi-square tests for linear trend (1 degree of freedom) were used to assess temporal trends in rates. P values were interpreted cautiously on the basis of a priori knowledge and the size of the effect.
Privacy considerations required the suppression of cells with small values (one to four). All analyses were carried out using SAS software version 9.2 (SAS Institute, Cary, NC). Because the study was based on anonymized data and conducted under the surveillance mandate of the Public Health Agency of Canada, ethics approval was not sought.
RESULTS
The study population included 3 882 790 deliveries between 2003 and 2016, of which 1 418 545 occurred between 2012 and 2016.
Composite Severe Maternal Morbidity
The rate of composite SMM was 16.1 (95% CI 15.9–16.3) per 1000 deliveries for the period 2012-2016 (22 799 cases (Table 1). The highest SMM rates were observed in the Yukon and Nunavut in 2012-2016 (Table 2). Rates of composite SMM were significantly higher in Newfoundland and Labrador, Nova Scotia, New Brunswick, Manitoba, Saskatchewan, the Yukon, and Nunavut compared with the rest of Canada, whereas rates were significantly lower in Alberta and British Columbia (Table 2).
Table 1Numbers and rates per 1000 deliveries (and their 95% confidence intervals) of composite severe maternal morbidity in Canada (excluding Québec), 2012-2016
Table 2Rates and rate ratios (with 95% confidence intervals) for composite severe maternal morbidity by province and territory, Canada (excluding Quebec), 2012-2016
Severe Preeclampsia, HELLP Syndrome, and Eclampsia
Severe preeclampsia, HELLP syndrome, and eclampsia comprised the most common SMM type. Overall rates did not change between 2012 and 2016 (Figure A, Table 3), although rates of eclampsia alone declined significantly (online Appendix Tables S2–S5). Rates of severe preeclampsia, HELLP syndrome, and eclampsia in 2012-2016 were significantly higher in Nova Scotia, New Brunswick, British Columbia, and Nunavut and significantly lower in Ontario and the Northwest Territories compared with the rest of Canada (online Appendix Table S4). The proportion of women with eclampsia expressed as a proportion of women with severe preeclampsia, HELLP syndrome, and eclampsia was 8.4% in Canada in 2012-2016 (online Appendix Table S6).
FigureTemporal trends in different types of severe maternal morbidity, Canada (excluding Québec), 2003-2016. (A) Severe (Sev.) preeclampsia, HELLP (hemolysis, elevated liver enzymes, low platelet count) syndrome, eclampsia, ICU (intensive care unit) admission, and sepsis (data on severe preeclampsia, HELLP syndrome, and eclampsia available for years 2012-2016 only. (B) Severe hemorrhage, hysterectomy, and cardiac conditions. (C) Embolism, shock, disseminated intravascular coagulation (DIC) severe uterine rupture, surgical complications. (D) Assisted ventilation, acute renal failure, dialysis, cerebrovascular accident.
Temporal trend in severe hemorrhage and surgical complications increased significantly from 2003 to 2012 (P value for trend <0.0001) and then decreased significantly from 2012 to 2016 (P value for trend <0.0001).
Rate
44.8
62.4
59.5
43.3
42.9
41.8
0.62–0.72
0.86–1.01
Maternal ICU admission: number
596
522
551
519
574
563
1.08
0.19
0.82
0.0005
Rate
24.1
18.4
19.6
18.3
20.1
19.8
0.96–1.21
0.73–0.92
Surgical complications: number
349
620
542
578
535
477
0.77
<0.0001
1.19
<0.0001
Rate
14.1
21.8
19.2
20.3
18.8
16.8
0.68–0.87
1.04–1.36
Hysterectomy: number
313
433
393
403
430
450
1.04
0.32
1.25
<0.0001
Rate
12.7
15.3
14.0
14.2
15.1
15.8
0.91–1.18
1.08–1.44
Sepsis: number
426
257
260
284
251
244
0.95
0.45
0.50
<0.0001
Rate
17.2
9.1
9.2
10.0
8.8
8.6
0.80–1.13
0.43–0.58
Embolism, shock, DIC: number
132
201
185
146
220
221
1.10
0.10
1.46
0.0001
Rate
5.3
7.1
6.6
5.1
7.7
7.8
0.91–1.33
1.17–1.81
Assisted ventilation: number
67
186
181
156
211
206
1.11
0.12
2.67
<0.0001
Rate
2.7
6.6
6.4
5.5
7.4
7.2
0.91–1.35
2.03–3.52
Cardiac conditions: number
163
177
178
162
194
176
0.99
0.79
0.94
0.32
Rate
6.2
6.2
6.3
5.7
6.8
6.2
0.81–1.22
0.76–1.16
Acute renal failure: number
43
102
119
101
158
167
1.63
<0.0001
3.38
<0.0001
Rate
1.7
3.6
4.2
3.6
5.5
5.9
1.28–2.09
2.42–4.72
Severe uterine rupture: number
27
35
40
35
49
45
1.28
0.16
1.45
0.003
Rate
0.9
1.2
1.4
1.2
1.7
1.6
0.83–2.00
0.90–2.34
Cerebrovascular accident: number
13
25
21
29
22
39
1.56
0.08
2.61
0.0004
Rate
0.53
0.88
0.75
1.02
0.77
1.37
0.94–2.57
1.39–4.89
DIC: disseminated intravascular coagulation; HELLP: hemolysis, elevated liver enzymes, low platelet count syndrome; ICU: intensive care unit; SPE: severe preeclampsia.
a See online Appendix Table S1 for the severe maternal morbidity subtypes included under each type of severe maternal morbidity.
b Temporal trend in severe hemorrhage and surgical complications increased significantly from 2003 to 2012 (P value for trend <0.0001) and then decreased significantly from 2012 to 2016 (P value for trend <0.0001).
Bold numbers indicate that the rate in the province or territory was significantly different (P value <0.05) from the rate in the rest of Canada (excluding Québec).
See online Appendix Table S1 for the severe maternal morbidity subtypes included under each type of severe maternal morbidity.
NL
PE
NS
NB
ON
MB
SK
AB
BC
NT
YT
NU
Number of deliveries
22 103
6745
41 320
33 460
674 688
80 514
74 648
264 658
210 612
3299
2070
3968
SPE, HELPP, eclampsia: number
123
35
312
267
3583
430
390
1414
1315
8
10
32
Rate
55.6
51.9
75.5↑
79.8↑
53.1↓
53.4
52.2
53.4
62.4↑
24.2↓
48.3
80.6↑
Severe hemorrhage: number
165
32
237
231
3,732
450
614
1071
439
27
22
61
Rate
74.7↑
47.4
57.4↑
69.0↑
55.3↑
55.9↑
82.3↑
40.5↓
20.8↓
81.8↑
106.3↑
153.7↑
Maternal ICU admission: number
65
6
41
129
1552
96
150
395
268
11
6
5
Rate
29.4
8.9
9.9↓
38.6↑
23.0↑
11.9↓
20.1
14.9↓
12.7↓
33.3
29.0
12.6
Surgical complications: number
36
9
73
64
1084
287
119
560
488
7
13
9
Rate
16.3
13.3
17.7
19.1
16.1↓
35.6↑
15.9↓
21.2↑
23.2↑
21.2
62.8↑
22.7
Hysterectomy: number
23
20
30
36
1074
90
95
433
298
<5
<5
<5
Rate
10.4
29.7↑
7.3↓
10.8↓
15.9↑
11.2↓
12.7
16.4↑
14.1
—
—
—
Sepsis: number
17
10
24
16
544
98
74
197
301
6
7
<5
Rate
7.7
14.8
5.8↓
4.8↓
8.1↓
12.2↑
9.9
7.4↓
14.3↑
18.2
33.8↑
—
Embolism, shock, DIC: number
13
<5
28
18
420
52
60
205
166
0
<5
7
Rate
5.9
—
6.8
5.4
6.2↓
6.5
8.0
7.7↑
7.9↑
0.0
—
17.6↑
Assisted ventilation: number
15
<5
20
11
506
50
62
149
116
0
<5
<5
Rate
6.8
—
4.8
3.3↓
7.5
6.2
8.3
5.6↓
5.5
0.0
—
—
Cardiac conditions: number
12
<5
27
16
450
50
52
153
110
<5
<5
6
Rate
5.4
—
6.5
4.8
6.7↑
6.2
7.0
5.8
5.2↓
—
—
15.1↑
Acute renal failure: number
11
<5
9
16
259
27
30
144
144
0
<5
0
Rate
5.0
3.0
2.2↓
4.8
3.8↓
3.4
4.0
5.4↑
6.8↑
0.0
—
0.0
Severe uterine rupture: number
<5
<5
5
7
125
15
16
14
15
<5
0
0
Rate
—
—
1.2
2.1
1.9↑
1.9
2.1
0.5↓
0.7↓
—
0.0
0.0
Cerebrovascular accident: number
<5
0
<5
0
72
10
7
26
15
0
0
<5
Rate
—
0.0
—
0.0
1.1
1.2
0.9
1.0
0.7
0.0
0.0
—
DIC: disseminated intravascular coagulation; HELLP: hemolysis, elevated liver enzymes, low platelet count syndrome; ICU: intensive care unit; SPE: severe preeclampsia; ↓: the rate was significantly lower; ↑: the rate was significantly higher (rate ratios in online Appendix Table S4).
a See online Appendix Table S1 for the severe maternal morbidity subtypes included under each type of severe maternal morbidity.
b Bold numbers indicate that the rate in the province or territory was significantly different (P value <0.05) from the rate in the rest of Canada (excluding Québec).
Severe hemorrhage was also relatively common, and rates did not change from 2003 to 2016. However, the temporal pattern was unexpected: Rates increased from 2003 to 2012 before declining (Figure B, Table 3). Temporal trends in severe hemorrhage subtypes showed that severe postpartum hemorrhage was largely responsible for the overall pattern in severe hemorrhage (online Appendix Table S2). In 2012-2016, rates of severe hemorrhage were significantly higher in Newfoundland and Labrador, Nova Scotia, New Brunswick, Ontario, Manitoba, Saskatchewan, Northwest Territories, the Yukon, and Nunavut compared with the rest of Canada, whereas rates were significantly lower in Alberta and British Columbia (online Appendix Table S4).
Intensive Care Unit Admission
Maternal ICU admissions declined between 2003 and 2016 (Figure A, Table 3). ICU admission in 2012-2016 was significantly more common in New Brunswick and Ontario compared with the rest of Canada and significantly less frequent in Nova Scotia, Manitoba, Alberta, and British Columbia (online Appendix S2–S5).
Appendix Table S1Severe maternal morbidity (SMM) types, subtypes, and International Classification of Diseases (ICD-10CA) and Canadian Classification of Interventions (CCI) codes for identifying each severe morbidity subtype
SMM type
SMM subtype
ICD-10CA, CCI codes and other variables
SPE, HELLP, eclampsia
Severe pre-eclampsia, HELLP syndrome
O14.1, O14.2
Eclampsia
O15
Severe hemorrhage
Placenta previa with hemorrhage and red cell transfusion
O44.1 + RBCTRNSF=‘Y’
Placental abruption with coagulation defect
O45.0
Antepartum hemorrhage with coagulation defect
O46.0
Intrapartum hemorrhage with coagulation defect
O67.0
Intrapartum hemorrhage with red cell transfusion
O67 + RBCTRNSF=‘Y’
Postpartum hemorrhage with red cell transfusion, procedures to the uterus or hysterectomy
O72 + any of the following: • RBCTRNSF=‘Y’, or • (1.RM.13, 1.KT.51, 5.PC.91.LA or 5.PC.91.HV) + RBCTRNSF = 1, or • (5.MD.60.RC, 5.MD.60.RD, 5.MD.60.KE, 5.MD.60.CB or 1.RM.89.LAb), or • 1.RM.87.LA-GX bNote: 1.RM.89.LA is included only if codes 1. PL.74, 1.RS.74 or 1.RS.80 are NOT also present
Curettage with red cell transfusion
(5.PC.91.GA, 5.PC.91.GC or 5.PC.91.GD) + RBCTRNSF=‘Y’
Maternal ICU admission
Maternal ICU admission
FTSPCU in (‘10’,’20’,’25’,’30’,’35’,’40’,’45’,’60’, ‘80’)
Surgical complications
Complications of obstetric surgery and procedures
O75.4
Evacuation of incisional hematoma with RBC transfusion
5.PC.73.JS + RBCTRNSF=‘Y’
Repair of bladder, urethra, or intestine
5.PC.80.JR, 1.NK.80 or 1.NM.80
Reclosure of caesarean wound with RBC transfusion
(5.PC.80.JM or 5.PC.80.JH) + RBCTRNSF=‘Y’
Hysterectomy
Caesarean hysterectomy
5.MD.60.RC, 5.MD.60.RD, 5.MD.60.KE, 5.MD.60.CB
Hysterectomy using an open approach (without bladder neck suspension, suspension of vaginal vault or pelvic floor repair)
1.RM.89.LAc (exclude if 1.PL.74, 1.RS.74 or 1.RS.80 code also present) or 1.RM.87.LA-GX
Note: 1.RM.89.LA is included only if codes 1.PL.74, 1.RS.74 or 1.RS.80 are NOT also present
Sepsis
Puerperal sepsis
O85
Septicemia during labour
O75.3
Embolism, shock, DIC
Obstetric shock
O75.1, R57, T80.5 or T88.6
Obstetric embolism
O88
Disseminated intravascular coagulation
D65
Assisted ventilation
Assisted ventilation through endotracheal tube
1.GZ.31.CA-ND
Assisted ventilation through tracheostomy
1.GZ.31.CR-ND
Cardiac conditions
Cardiac complications of anesthesia
O74.2, O89.1
Cardiomyopathy
O90.3, I42, I43
Cardiac arrest and resuscitation
I46, I49.0, 1.HZ.09, 1.HZ.30
Myocardial infarction
I21, I22
Pulmonary edema and heart failure
I50, J81
Acute renal failure
Acute renal failure
O90.4, N17, N19 or N99.0
Dialysis
1.PZ.21
Severe uterine rupture
Rupture of the uterus with red cell transfusion, procedures to the uterus or hysterectomy
(O71.0 or O71.1) + any of the following: • RBCTRNSF=‘Y’, or • (1.RM.13, 1.KT.51, 5.PC.91.LA or 5.PC.91.HV) + RBCTRNSF=‘Y’, or • (5.MD.60.RC, 5.MD.60.RD, 5.MD.60.KE, 5.MD.60.CB or 1.RM.89.LAa), or • 1.RM.87.LA-GX aNote: 1.RM.89.LA is included only if codes 1. PL.74, 1.RS.74 or 1.RS.80 are NOT also present
Cerebrovascular accidents
Cerebral venous thrombosis in pregnancy
O22.5
Cerebral venous thrombosis in the puerperium
O87.3
Subarachnoid and intracranial hemorrhage, cerebral infarction
I60, I61, I62, I63 or I64
Other types
Acute fatty liver with red cell transfusion or plasma transfusion
O26.6 + (RBCTRNSF=‘Y’ or PLSTRNSF=’Y’)
Hepatic failure
K71 or K72
Cerebral edema or coma
G93.6 or R40.2
Pulmonary, cardiac, and CNS complications of anesthesia during pregnancy, labour, delivery or the puerperium
Surgical or manual correction of inverted uterus for vaginal births only
5.PC.91.HQ or 5.PC.91.HP, restricted to vaginal births (i.e., absence of caesarean code 5.MD.60)
Sickle cell anemia with crisis
D57.0
Acute psychosis
F53.1 or F23
Status epilepticus
G41
HIV disease
B20-24, O98.7
Notes on selected diagnostic and procedure codes
• Canadian Institute for Health Information coding specific to severe preeclampsia and HELLP (O14.1 and O14.2) began in 2012. The conditions under acute fatty liver (O26.6) - were expanded in ICD-10-CA version 2009, to add codes for the sixth digits of “2” (Delivered, with mention of postpartum complication) and “4” (Postpartum condition or complication). Previously postpartum liver disorders may have been captured at O90.802 and O90.804 Other complications of the puerperium, not elsewhere classified, respectively. In addition, in ICD-10-CA version 2009 the conditions included in this code were expanded to include “Cholestasis (intrahepatic) in pregnancy” and “Obstetric cholestasis.” Previously, cholestasis in pregnancy would have been classified as O99.6 Diseases of the digestive system complicating pregnancy, childbirth and the puerperium which included conditions in K80-K93, and more specifically, K83.1 Cholestasis NEC.
• The CCI code 5.PC.91.HV Interventions to uterus (following delivery or abortion), compression using intrauterine balloon was introduced in CCI version 2012. Previously, this intervention may have been captured by code 5.PC.91.HT Interventions to uterus (following delivery or abortion) uterine (and vaginal) packing.
Appendix Table S2Temporal trends in severe maternal morbidity subtypes, Canada (excluding Quebec), 2003 to 2016 (rates expressed per 10,000 deliveries)
Severe maternal morbidity subtypes
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
P for trend
Severe preeclampsia, and HELLP syndrome
-
-
-
-
-
-
-
-
-
51.3
53.6
51.0
51.5
49.9
0.24
Eclampsia
12.3
10.7
9.5
6.6
5.7
6.1
5.9
5.5
5.6
4.9
4.9
4.5
4.0
5.3
<0.0001
Placenta previa with hemorrhage with red cell transfusion
3.9
3.7
4.1
3.4
3.9
4.5
4.9
5.3
4.6
5.0
5.3
2.8
2.8
2.9
0.12
Placental abruption with coagulation defect
2.1
1.7
1.9
1.3
1.6
1.7
2.0
1.6
1.4
1.9
1.7
2.4
2.0
1.6
0.52
Antepartum hemorrhage with coagulation defect
0.65
0.84
0.42
0.26
0.60
0.60
0.63
0.57
0.39
0.46
0.63
0.45
0.38
0.84
0.90
Intrapartum hemorrhage with coagulation defect
1.2
0.73
1.1
0.73
0.71
0.81
0.77
0.78
0.57
0.91
0.78
0.59
0.80
0.70
0.06
Intrapartum hemorrhage with red cell transfusion
2.8
2.1
2.6
2.1
1.7
2.2
1.8
2.5
1.9
3.5
3.2
2.1
1.9
1.7
0.62
Postpartum hemorrhage with red cell transfusion, procedures to the uterus or hysterectomy
Appendix Table S4Rate ratios and 95% confidence intervals expressing the relative rate of severe maternal morbidity types in each province/territory compared with the rest of Canada (excluding Quebec), Canada, 2012-2016
Severe maternal morbidity category/ Province or territory
NL
PE
NS
NB
ON
MB
Severe pre-eclampsia, eclampsia, HELLP
Rate ratio
1.00
0.93
1.37
1.44
0.91
0.95
95% CI
0.83-1.19
0.67-1.29
1.22-1.53
1.28-1.63
0.87-0.95
0.87-1.05
P value
0.99
0.72
<0.0001
<0.0001
<0.0001
0.35
Severe hemorrhage
Rate ratio
1.51
0.95
1.15
1.40
1.23
1.13
95% CI
1.29-1.76
0.67-1.34
1.01-1.31
1.22-1.59
1.17-1.29
1.03-1.24
P value
<0.0001
0.84
0.03
<0.0001
<0.0001
0.01
Maternal ICU admission
Rate ratio
1.54
0.46
0.51
2.06
1.46
0.61
95% CI
1.21-1.97
0.21-1.03
0.37-0.69
1.72-2.45
1.35-1.57
0.50-0.74
P value
0.0006
0.07
<0.0001
<0.0001
<0.0001
<0.0001
Surgical complications
Rate ratio
0.84
0.69
0.91
0.99
0.72
1.94
95% CI
0.60-1.16
0.36-1.32
0.72-1.15
0.77-1.26
0.66-0.77
1.71-2.19
P value
0.33
0.32
0.45
0.96
<0.0001
<0.0001
Hysterectomy
Rate ratio
0.70
2.00
0.48
0.72
1.14
0.74
95% CI
0.46-1.05
1.29-3.11
0.34-0.69
0.52-1.00
1.05-1.25
0.60-0.92
P value
0.10
0.003
<0.0001
0.05
0.002
0.006
Sepsis
Rate ratio
0.84
1.63
0.63
0.52
0.80
1.36
95% CI
0.52-1.35
0.87-3.03
0.42-0.94
0.32-0.85
0.71-0.89
1.11-1.67
P value
0.54
0.18
0.02
0.006
<0.0001
0.004
Embolism, shock, DIC
Rate ratio
0.86
0.22
0.99
0.78
0.84
0.94
95% CI
0.50-1.48
0.03-1.53
0.68-1.44
0.49-1.24
0.74-0.95
0.71-1.24
P value
0.67
0.15
0.97
0.35
0.007
0.71
Assisted ventilation
Rate ratio
1.03
0.67
0.73
0.49
1.29
0.93
95% CI
0.62-1.71
0.22-2.08
0.47-1.13
0.27-0.89
1.13-1.46
0.70-1.24
P value
0.92
0.65
0.18
0.02
0.0001
0.69
Cardiac conditions
Rate ratio
0.87
0.95
1.05
0.76
1.15
1.00
95% CI
0.49-1.54
0.36-2.54
0.72-1.54
0.47-1.25
1.00-1.31
0.75-1.33
P value
0.73
0.88
0.76
0.32
0.05
0.96
Acute renal failure
Rate ratio
1.10
0.65
0.47
1.05
0.74
0.73
95% CI
0.60-1.99
0.16-2.61
0.24-0.91
0.64-1.73
0.63-0.87
0.49-1.07
P value
0.88
0.75
0.03
0.94
0.0002
0.12
Severe uterine rupture
Rate ratio
1.26
2.07
0.84
1.47
1.74
1.32
95% CI
0.47-3.40
0.51-8.34
0.34-2.03
0.69-3.12
1.32-2.31
0.78-2.23
P value
0.56
0.25
0.85
0.35
0.0001
0.29
Cerebrovascular accidents
Rate ratio
0.95
0.00
0.50
0.00
1.26
1.33
95% CI
0.24-3.84
-
0.12-2.02
-
0.90-1.77
0.70-2.53
P value
0.78
0.86
0.46
0.08
0.20
0.35
Severe maternal morbidity category/ Province or territory
SK
AB
BC
NT
YU
NU
Severe pre-eclampsia, eclampsia, HELLP
Rate ratio
0.93
0.95
1.14
0.43
0.86
1.45
95% CI
0.84-1.03
0.89-1.00
1.08-1.21
0.22-0.87
0.47-1.61
1.02-2.04
P value
0.18
0.07
<0.0001
0.02
0.75
0.04
Severe hemorrhage
Rate ratio
1.71
0.78
0.38
1.64
2.13
3.10
95% CI
1.57-1.86
0.73-0.83
0.34-0.42
1.13-2.39
1.41-3.23
2.41-3.98
P value
<0.0001
<0.0001
<0.0001
0.02
0.0005
<0.0001
Maternal ICU admission
Rate ratio
1.05
0.74
0.63
1.74
1.51
0.66
95% CI
0.89-1.24
0.66-0.82
0.55-0.71
0.96-3.14
0.68-3.36
0.27-1.57
P value
0.60
<0.0001
<0.0001
0.10
0.44
0.44
Surgical complications
Rate ratio
0.81
1.11
1.24
1.09
3.25
1.17
95% CI
0.68-0.98
1.02-1.22
1.12-1.36
0.52-2.30
1.89-5.60
0.61-2.25
P value
0.03
0.02
<0.0001
0.97
<0.0001
0.77
Hysterectomy
Rate ratio
0.85
1.13
0.94
0.61
0.65
0.68
95% CI
0.69-1.04
1.01-1.25
0.84-1.07
0.20-1.90
0.16-2.60
0.25-1.81
P value
0.13
0.03
0.36
0.39
0.54
0.56
Sepsis
Rate ratio
1.09
0.78
1.73
1.99
3.71
0.55
95% CI
0.86-1.38
0.67-0.91
1.52-1.97
0.89-4.45
1.77-7.80
0.14-2.20
P value
0.51
0.002
<0.0001
0.13
0.0008
0.60
Embolism, shock, DIC
Rate ratio
1.18
1.16
1.18
0.00
1.41
2.59
95% CI
0.91-1.54
1.00-1.36
1.00-1.40
-
0.35-5.64
1.23-5.43
P value
0.23
0.05
0.05
0.18
0.66
0.02
Assisted ventilation
Rate ratio
1.27
0.82
0.81
0.00
2.19
1.52
95% CI
0.98-1.65
0.69-0.98
0.67-0.98
-
0.71-6.80
0.57-4.07
P value
0.08
0.03
0.03
0.29
0.16
0.34
Cardiac conditions
Rate ratio
1.13
0.91
0.82
0.97
0.78
2.44
95% CI
0.85-1.49
0.77-1.09
0.67-1.00
0.24-3.90
0.11-5.51
1.09-5.44
P value
0.45
0.33
0.05
0.76
0.85
0.04
Acute renal failure
Rate ratio
0.88
1.26
1.65
0.00
2.13
0.00
95% CI
0.61-1.27
1.04-1.51
1.37-1.99
-
0.53-8.53
-
P value
0.55
0.02
<0.0001
0.41
0.24
0.43
Severe uterine rupture
Rate ratio
1.53
0.32
0.46
2.11
0.00
0.00
95% CI
0.92-2.55
0.19-0.55
0.27-0.77
0.30-15.1
-
-
P value
0.11
<0.0001
0.002
0.38
0.71
0.93
Cerebrovascular accidents
Rate ratio
0.98
1.04
0.72
0.00
0.00
2.66
95% CI
0.46-2.11
0.68-1.59
0.42-1.23
-
-
0.37-19.0
P value
0.88
0.95
0.28
0.74
0.49
0.84
Statistically significant differences indicated by bold text.
Appendix Table S6Women with eclampsia expressed as a proportion (%) of women with severe pre-eclampsia, HELLP syndrome and eclampsia, provinces/territories Canada (excluding Quebec) 2012-2016
Surgical complications showed a pattern somewhat similar to that of severe hemorrhage (Figure C, Table 3), although the rate in 2016 was 19% higher than the rate in 2003. Complications of obstetric surgery and procedures increased and then decreased; evacuation of incisional hematoma with red cell transfusion declined steadily; rates of repair of the bladder, urethra, or intestine rose significantly, whereas rates of re-closure of the Caesarean wound with red cell transfusion remained stable (online Appendix Table S2). In 2012-2016, surgical complications were significantly more common in Manitoba, Alberta, British Columbia, and the Yukon and significantly less frequent in Ontario and Saskatchewan (online Appendix Table S4).
Hysterectomy
Hysterectomy rates increased between 2003 and 2016 but were stable between 2012 and 2016 (Figure B, Table 3). Caesarean hysterectomy increased, whereas hysterectomy for postpartum hemorrhage by the open approach remained stable (online Appendix Table S2). Hysterectomy rates were significantly higher in Prince Edward Island, Ontario, and Alberta and significantly lower in Nova Scotia, New Brunswick, and Manitoba than in the rest of Canada (online Appendix Table S4).
Sepsis
Sepsis rates declined significantly (Figure A, Table 3); the puerperal sepsis subtype declined substantially, whereas septicemia in labour remained stable (online Appendix Table S2). Sepsis rates in 2012-2016 were significantly higher in Manitoba, British Columbia, and the Yukon and significantly lower in Nova Scotia, New Brunswick, Ontario, and Alberta compared with the rest of Canada (online Appendix Table S4).
Embolism, Shock, and Disseminated Intravascular Coagulation
Rates of obstetric embolism, shock, and DIC increased; stratified analyses showed that obstetric embolism and obstetric shock increased significantly, whereas DIC rates did not change. The rate of this SMM type in 2012-2016 was significantly higher in Alberta, British Columbia, and Nunavut and significantly lower in Ontario.
Assisted Ventilation
Rates of assisted ventilation increased (Figure D, Table 3). Rates of assisted ventilation were significantly lower in New Brunswick and Alberta than in the rest of Canada (online Appendix Table S4).
Cardiac Conditions
Rates of cardiac conditions remained unchanged overall. Cardiac SMM subtypes, such as cardiomyopathy, rose significantly over the 14 years, whereas pulmonary edema and heart failure rates declined significantly, and the frequency of cardiac complications of anaesthesia, cardiac arrest and resuscitation, and myocardial infarction remained unchanged (online Appendix Table S2). The frequency of cardiac conditions was significantly higher in Ontario and Nunavut and significantly lower in British Columbia in 2012-2016 (online Appendix Table S4).
Acute Renal Failure
Acute renal failure and dialysis increased substantially (Figure D, Table 3). Rates in 2012-2016 were significantly higher in Alberta and British Columbia and significantly lower in Nova Scotia and Ontario compared with the rest of Canada (online Appendix Table S4).
Severe Uterine Rupture
Severe uterine rupture showed a small and increasing temporal trend (Figure C, Table 3). Rates of severe uterine rupture in 2012-2016 were significantly higher in Ontario than in the rest of Canada and significantly lower in Alberta and British Columbia (online Appendix Table S4).
Cerebrovascular Accidents
Cerebrovascular accidents increased, and two subtypes (stroke and cerebral venous thrombosis in pregnancy) showed a significant temporal increase (online Appendix Table S2). Stroke rates in 2012-2016 showed no significant regional variation.
Miscellaneous Severe Maternal Morbidity
Acute fatty liver with red cell or plasma transfusion, sickle cell crisis, status epilepticus, and human immunodeficiency virus infection showed significant increases from 2003 to 2016, whereas status asthmaticus, adult respiratory distress syndrome, surgical or manual correction of an inverted uterus, and acute psychosis showed a significant decline (online Appendix Table S2). Rates of surgical or manual correction of an inverted uterus were unexpectedly high in Nunavut in 2012-2016.
DISCUSSION
Our study provides a comprehensive overview of temporal trends and regional variations in SMM in Canada (excluding Québec) from 2012 to 2016 and temporal trends in SMM from 2003 to 2016. The results include a sequential rise and fall in rates of severe hemorrhage and surgical complications over the 14-year period. Because severe hemorrhage was one of the most common SMM types, the recent reduction in this severe morbidity resulted in a temporal reduction in composite SMM between 2012 and 2016. Stroke, severe uterine rupture, embolism, shock and DIC, acute renal failure, hysterectomy, surgical complications, and assisted ventilation rates rose significantly between 2003 and 2016; rates of cardiac conditions were stable; and sepsis and maternal ICU admission rates declined significantly. Some of the changes in SMM types concealed disparate changes in component subtypes. Thus, the stability in overall cardiac conditions between 2003 and 2016 obscured rising rates of cardiomyopathy and declining rates of pulmonary edema and heart failure. Interprovincial and territorial comparisons showed significant differences in rates of composite SMM and SMM types and subtypes and suggested regional priorities for clinical and public health initiatives.
The diverse SMM trends and regional variations presented in this paper require careful study. A brief discussion of some important findings is attempted here, with a more detailed discussion provided in the online Appendix. Rates of eclampsia in Canada
declined in a nearly monotonic pattern to 5.3 per 10 000 deliveries in 2016 (online Appendix Table S2). These rates were similar to the 5.6 per 10 000 reported in the United Kingdom in 2012-2013,
Trends in postpartum hemorrhage in high resource countries: a review and recommendations from the International Postpartum Hemorrhage Collaborative Group.
although epidemiologic investigations have failed to pinpoint a cause. The more recent fall in severe postpartum hemorrhage rates since 2012 is a welcome development, although the cause of this decline is equally unclear. Detailed studies are required to examine possible causes for the decline, including the increased use of tranexamic acid,
because the potential for prevention is evident in the widely varying regional rates of severe hemorrhage.
Increases in rates of repair of the bladder, urethra, and intestine are concerning. Bladder and intestinal injuries may be related to the increase in Caesarean deliveries and in deliveries to women with a previous Caesarean section, whereas injuries to the urethra may be a consequence of the restricted use of episiotomy.
Obstetric embolism rates in 2012 and 2013 in Canada (excluding Québec) of 2.9 and 3.0 per 10 000 deliveries were similar to those reported from the United Kingdom in the same years (2.7 per 10 000 deliveries
and it has been shown to be restricted to women with preeclampsia and other hypertensive disorders of pregnancy. The rise is likely the result of fluid management protocols for women with preeclampsia. Curtailment of fluid intake in an attempt to prevent pulmonary edema may be increasing the risk of acute renal failure in some Canadian jurisdictions.
In support of that explanation, provinces with relatively high rates of acute renal failure in 2012-2016 (i.e., Alberta and British Columbia) also had relatively low rates of pulmonary edema and heart failure (online Appendix Table S5).
Other concerning trends include the temporal increase in cardiomyopathy (which may be related to increases in substance abuse and obesity
), severe uterine rupture, and cerebrovascular accidents. The rising trend in severe uterine rupture noted in this study does not appear to be related to increases in attempted vaginal birth after Caesarean section (VBAC; which decreased from 34.0% in 2003 to 31.4% in 2014).
Rather, the rise may have been related to changes in the selection of candidates for attempted VBAC or changes in the expertise of health care providers because severe neonatal complications following attempted VBAC also increased over the study period.
Finally, the rise in cerebrovascular accidents appears to be unrelated to increases in maternal age. A recent study by the Canadian Perinatal Surveillance System showed that most strokes occurred in the postpartum period and were strongly associated with hypertensive disorders of pregnancy,
a finding indicating a need for improved management of hypertensive disorders, especially in the postpartum period.
The strengths of our study include the comprehensive assessment of SMM by using a validated data source. Detailed temporal and regional comparisons provide information to guide clinicians and policy experts in identifying priority issues. Limitations of our study include shortcomings in the framework for SMM surveillance, which was based on ICD-10CA and CCI codes, and this may have failed to identify some SMM cases accurately. Our inability to include information from the province of Québec (which does not contribute to the Discharge Abstract Database) was another significant limitation of our study.
CONCLUSION
Health care providers and public health managers in the perinatal domain can use the evidence from our overview to improve quality of care and maternal health. Provinces and territories with high rates of specific SMM types and subtypes (e.g., severe hemorrhage, acute renal failure, sepsis, and surgical complication rates) should target these conditions with quality improvement initiatives. Similarly, increases in severe uterine rupture, obstetric embolism, and shock should be highlighted and addressed through appropriate changes in obstetric management. Finally, our report should stimulate future research to elucidate the causes underlying the temporal changes and regional differences we observed (i.e., the responsible maternal characteristics, clinical management, and health system factors).
Detailed discussion of temporal trends and regional variations
Severe pre-eclampsia, HELLP syndrome and eclampsia: This relatively common SMM type showed no temporal trend between 2012 and 2016. Eclampsia is preventable, and geographic variations can serve as a marker of differences in the availability and/or quality of obstetric services. Absolute rates of eclampsia in Canada [
] showed a near-monotonic decline from 12.4 in 2003 to a low of 4.0 in 2015 and 5.3 per 10,000 deliveries in 2016 (Appendix Table S2). Those rates were similar to the 5.6 per 10,000 reported in the United Kingdom in 2012-13 [
]). Within Canada, eclampsia rates were highest in Nunavut (15.1, 95% CI 5.5-32.9 per 10,000 deliveries) in 2012-2016.
Severe hemorrhage: The recent rise in rates of postpartum hemorrhage and severe postpartum hemorrhage in Canada and other high-income countries has been well documented [
Trends in postpartum hemorrhage in high resource countries: a review and recommendations from the International Postpartum Hemorrhage Collaborative Group.
], although epidemiologic investigations have failed to pinpoint a cause. The more recent fall in severe postpartum hemorrhage rates since 2012 is a welcome development, although the cause of this decline is equally unclear. Despite its decline since 2012, severe hemorrhage represents one of the most common types of SMM in Canada. Its potential for prevention is evident in the widely varying rates by province and territory: significantly higher in Newfoundland and Labrador, Nova Scotia, New Brunswick, Ontario, Manitoba, Saskatchewan and the 3 territories than in the rest of Canada.
ICU admission: Maternal admissions to ICU declined from 24.1 to 19.8 per 10,000 deliveries in 2003 vs 2016. The rate in 2003 was similar to the 24 per 10,000 deliveries reported in the Netherlands in 2004-2006 [
]. The observed interprovincial differences in rates of ICU admission may be due to the introduction of step-down units (which deliver a lower intensity of care than traditional ICUs) in some provinces.
Surgical complications: The rise and fall in this SMM type reflects the trend in its most common subtype: complications of obstetric surgery and procedures (ICD-10CA code O75.4). The latter subtype is heterogeneous (comprising cardiac arrest, cardiac failure or cerebral anoxia following caesarean delivery or other obstetric surgery or procedures, including delivery not otherwise specified, and also post-procedural renal failure and post-procedural disorders of the genitourinary system), thus clouding interpretation. Increases in rates of repair of the bladder, urethra and intestine are concerning, while reduction in rates of incisional hematoma requiring evacuation and transfusion are encouraging. Provinces/territories with higher rates of surgical complications included Manitoba, Alberta, British Columbia and the Yukon.
Hysterectomy: Rates of hysterectomy showed a significant rise, with a rate of 15.8 per 10,000 deliveries in 2016. Rates reported elsewhere were 2.2 in the United Kingdom in 2012-13 [
]. Within Canada, Prince Edward Island, Ontario and Alberta had significantly higher rates than the rest of Canada. British Columbia, previously reported to have low rates of postpartum hemorrhage with blood transfusion and high rates of hysterectomy in 2003 to 2007 [
], had relatively low rates of severe hemorrhage but rates of hysterectomy that were similar to those in the rest of Canada in 2012-2016.
Sepsis: Rates of sepsis continued the steady decline from previous years and likely reflect the antiseptic techniques and antibiotic prophylaxis regimens instituted in recent decades. However, rates of sepsis were significantly higher in Manitoba, British Columbia and the Yukon than in the rest of Canada. Sepsis rates of 9.0 and 9.3 per 10,000 deliveries in Canada in 2012 and 2013 were similar to sepsis rates of 10.3 in the United Kingdom in the same years [
Embolism, shock and DIC: Rates of obstetric embolism and shock rose significantly from 2003 to 2016, with the trend continuing in the most recent 5 years. Rates were significantly higher in Alberta, British Columbia and Nunavut compared with the rest of Canada. Obstetric embolism rates in 2012 and 2013 in Canada (excluding Quebec) of 2.9 and 3.0 per 10,000 deliveries were similar to those reported from the United Kingdom in those years (2.7 per 10,000 deliveries [
Acute renal failure: Rates of acute renal failure and dialysis increased markedly from 1.7 to 5.9 per 10,000 deliveries in 2003 vs 2016 in Canada and rates were significantly higher in Alberta and British Columbia compared with the rest of Canada. This adverse trend has been noted previously [
] and shown to be restricted to women with pre-eclampsia and other hypertensive disorders of pregnancy. The rise is likely due to fluid management protocols for women with pre-eclampsia. Curtailment of fluid intake in an attempt to prevent pulmonary edema may be increasing the risk of acute renal failure in some Canadian jurisdictions [
]. In support of that explanation, provinces with relatively high rates of acute renal failure in 2012-2016 (viz., Alberta and British Columbia) also had relatively low rates of pulmonary edema and heart failure (Appendix Table S5).
Cardiac conditions: Cardiac conditions have a high case fatality (40.6 per 1000 in 2012-16 [Dzakpasu S, Deb-Rinker P, Arbour L, et al. Severe maternal morbidity surveillance: monitoring pregnant women at high risk for prolonged hospitalization and death [submitted for publication]]), with the highest death rates occurring among those with cardiac arrest and resuscitation. This latter SMM subtype represents the terminal event of many heterogeneous pathologic processes; fortunately, its frequency is low. The observed temporal increase in cardiomyopathy is concerning, given its high mortality, and may be related to increases in substance abuse and obesity [
Assisted ventilation: Rates of assisted ventilation increased substantially, although no province/territory has significantly higher rates than the rest of Canada. Assisted ventilation rates of 7.2 per 10,000 deliveries in Canada in 2016 were higher than the 2.6 per 10,000 reported in the United Kingdom in 2012-2013 [
Severe uterine rupture: Rates of uterine rupture associated with red cell transfusion, procedures to the uterus or hysterectomy were relatively rare but showed a significant rise between 2003 and 2016. Uterine rupture is strongly associated with attempted vaginal birth after caesarean delivery (VBAC), but the rising trend in severe uterine rupture noted in this study does not appear to be related to increases in attempted VBAC (which decreased from 34.0% in 2003 to 31.4% in 2014 [
]). Rather, the rise may have been related to changes in selection of candidates for attempted VBAC and/or changes in the expertise of health care providers [
]. This speculation is supported by the fact that severe neonatal complications of attempted VBAC increased over the study period (adjusted rate ratios for neonatal mortality and severe neonatal morbidity associated with attempted VBAC compared with elective repeat caesarean increased from 0.94, 95% CI 0.77-1.15 in 2003-05 to 2.07, 95% CI 1.83-2.35 in 2012-14 [
Cerebrovascular accidents: The rates of cerebrovascular accidents and of cerebral thrombosis in pregnancy have increased, especially in recent years. A recent study by the Canadian Perinatal Surveillance System showed that adjustment for maternal age did not abolish the temporal rise in stroke rates [
Dayan N, Fell DB, Guo Y, et al. Severe maternal morbidity in women with high BMI in IVF and unassisted singleton pregnancies [e-pub ahead of print]. Hum Reprod doi: 10.1093/humrep/dey224, accessed March 27, 2019.
Trends in postpartum hemorrhage in high resource countries: a review and recommendations from the International Postpartum Hemorrhage Collaborative Group.
cells with small numerators (>0 and <5) suppressed.
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