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Table 1 Summary of included studies with reference numbers. N = 81 [3, 8, 16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94]

From: A scoping review of severe maternal morbidity: describing risk factors and methodological approaches to inform population-based surveillance

Study Characteristic Reference Number
Number and data source of included studies
 USa data (n = 50)
  National Inpatient Sample 17,18,26,39,45,48,58,72
  National Readmission Database: 21 states 32
  CMSb Medicaid (MAX) data 22
  US claims data 27,70
  US perinatal data networks 28,43
  Hospital discharge data: 7 states 33
  Hospital discharge data: Illinois 84
  Hospital discharge data: Maryland 81
  Hospital discharge ± birth certificate data: New York State 19,44,53
  Hospital discharge + birth certificate data: 3 states 29
  Hospital discharge + birth certificate data: Iowa 38
  Hospital discharge + birth certificate data: New York City 46,47,49,50,78
  Hospital discharge, birth, ± death certificate data: California 36,40,52,55-57,68,69,76
  Hospital discharge, birth, + death certificate data: Georgia 91
  Hospital discharge, birth, ± death certificate data: Washington 42,62–64
  Hospital discharge + medical record data: 16 California hospitals 51
  Hospital discharge + medical record data: Massachusetts 21
  Hospital discharge + SARTc + vital statistics data: Massachusetts 23
  Birth certificate data: Ohio 71
  Birth certificate and SART data: 8 states 67
  Medical record data single hospital: California 93
  Medical record data single hospital: New York 73
  Medical record data single hospital: Missouri 83
  Medical record data single hospital: Tennessee 41
 Non-US data (n = 31)
  Multiple countries including US 60
  Multiple countries not including US 90
  Japan 16
  Korea 75
  Sweden 92
  Finland 77
  France 25,54,88
  Canada: Ontario 34,35,80,89
  Canada: British Columbia 61,85,86
  Canada: multiple provinces 3,8,65,66,74,79,94
  Australia: New South Wales 20,24,30,31,37,82,87
  Australia: Victoria 59
Study design and population
 Study design nested case-control (n = 6)
  Yes 16,21,34,42,54,88
 Hospital-level risk factors with specific hypotheses (n = 8)
  Patient-level data adjusted for clustering among hospitals 19,27,29,32,39
  Hierarchical models 36,91
  Hospital-level data 49
 Delivery discharges limited by: (n = 22)
  Community hospitals 36
  Annual delivery volume less than 1000 45
  Low risk 19,40,65,66
  Low risk breech presentation 24
  Medicaid eligibility 22
  Nulliparous 85
  Prior cesarean delivery with parity = 1 94
  Prior cesarean delivery ≥3 73
  No prior cesarean delivery 66
  Cesarean delivery 22–34 gestational weeks 25
  Elective cesarean delivery 16
  Preterm gestation 20,68
  Term laboring patients with prolonged second stage 74
  Preeclampsia 27
  Hemorrhage 80
  Race/ethnicity Hispanic or White 46
  Race Black or White 47,48
 SMMddefinition CDCe basis [7] (n = 37)
  25 indicators 17,18,23,29,33,36,38,42,46-53,58,60,68,69,71,72,75,76,91,93
  18 indicators 19,26,27,41,44,55-57,78,83,84
 SMM definition not using CDC basis (n = 44)
  Adapted from other US work (Bateman et al. [22]) 32,39,45,61–63
  Adapted from Canadian work (Wen et al. [3]/Joseph et al. [8]) 3,8,22,34,35,66,74,89,94
  Adapted from Australian work (Roberts et al. [8]) 20,24,30,31,37,59,79,82,87
  Adapted from Swedish work (Wahlberg et al. [92]) 90,92
  Adapted from Geller et al. (5 factor) [95] 43,85
  Death 80
  Intensive care unit admission 21,25,28,40,53,65,67,71,73
  Other 16,54,64,77,86,88
 Sensitivity analysis for use of transfusion in SMM definition (n = 15)
  Yes 26,33,38,44,46,47,49,50,55-57,60,78,91,94
 Blood transfusion threshold was 4 units of packed red blood cells (n = 6)
  Yes 43,51,54,85,88,93
 Blood transfusion not included in definition (n = 10)
  Yes 22,32,37,39,45,77,80,86,90,92
Key risk factors studied
 General risk factors (no hypotheses) (n = 16)
  Yes 3,8,22,38,42-45,52,53,59,60,80,81,83,90
 Patient-level risk factors with specific hypotheses (n = 57)
  Race/ethnicity 18,26,33,46-48,50,57,58,72
  BMIf or gestational weight gain 35,55,62,71,73,78,86,88
  Maternal age 63,76,85
  Preterm birth 25,51,68
  Infertility/IVFg/ARTh 23,34,54,67,70,93
  Preeclampsia 64
  Hemorrhage 37
  Obstructive sleep apnea 28
  Congenital heart disease 79
  Inflammatory bowel disease 87
  Autoimmunity 30
  Idiopathic arthritis 31
  Rural vs. urban 61
  Maternal birthplace or immigration country 89,92
  Amphetamine/opioid use 17
  Route of delivery 20,21,24,41,56,66,74,77,84,94
  Induction of labor 40,65,82
  Anesthesia for cesarean delivery 16
  Off-hours delivery 69,75
 Hospital-level risk factors with specific hypotheses (n = 8)
  Delivery volume 27,29,39
  Level of care 32,91
  Percent midwives delivering 19
  Presence of laborist 36
  Hospital quality indicators 49
  1. aUS United States; bCMS Centers for Medicare and Medicaid Services; cSociety for Assisted Reproductive Technology; dSMM severe maternal morbidity; eCDC Centers for Disease Control and Prevention; fBMI body mass index; gIVF in vitro fertilization; hART assisted reproductive technology