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Table 1 Severe maternal morbidity incidence using four indicators and the study populations’ characteristics (2003–2018)

From: Comparison of global indicators for severe maternal morbidity among South Korean women who delivered from 2003 to 2018: a population-based retrospective cohort study

  US-CDC’s SMM Gold standard guideline for SMMa Zwart et al.’s SMM EURONET-SAMM
No (n = 6,269,558)   Yes (n = 151,533)   P-value No (n = 6,221,001)   Yes (n = 200,090)   P-value No (n = 6,401,007)   Yes (n = 20,084)   P-value No (n = 6,333,639)   Yes (n = 87,452)   P-value
N % N % N % N % N % N % N % N %
Maternal age (y)
 15–19 23,179 96.4 862 3.6  < .0001 22,944 95.4 1,097 4.6  < .0001 23,983 99.8 58 0.2  < .0001 23,664 98.4 377 1.6  < .0001
 20–24 313,014 97.8 6,999 2.2   310,163 96.9 9,850 3.1   319,343 99.8 670 0.2   316,158 98.8 3,855 1.2  
 25–29 1,757,569 98.1 34,153 1.9   1,743,220 97.3 48,502 2.7   1,787,457 99.8 4,265 0.2   1,771,009 98.8 20,713 1.2  
 30–34 2,921,132 97.8 65,872 2.2   2,899,720 97.1 87,284 2.9   2,978,744 99.7 8,260 0.3   2,948,384 98.7 38,620 1.3  
 35–39 1,100,678 96.9 35,550 3.1   1,092,320 96.1 43,908 3.9   1,130,918 99.5 5,310 0.5   1,116,714 98.3 19,514 1.7  
 40–44 148,938 95.1 7,703 4.9   147,636 94.3 9,005 5.8   155,204 99.1 1,437 0.9   152,476 97.3 4,165 2.7  
 45 +  5,048 92.8 394 7.2   4,998 91.8 444 8.2   5,358 98.5 84 1.5   5,234 96.2 208 3.8  
Household income
 1Q (Low) 1,257,640 97.5 32,705 2.5  < .0001 1,247,497 96.7 42,848 3.3  < .0001 1,285,885 99.7 4,460 0.4  < .0001 1,271,599 98.6 18,746 1.5  < .0001
 2Q 1,590,797 97.7 38,155 2.3   1,578,391 96.9 50,561 3.1   1,623,749 99.7 5,203 0.3   1,606,787 98.6 22,165 1.4  
 3Q 2,211,770 97.7 51,557 2.3   2,194,855 97 68,472 3   2,256,625 99.7 6,702 0.3   2,233,451 98.7 29,876 1.3  
 4Q (High) 1,209,351 97.7 29,116 2.4   1,200,258 96.9 38,209 3.1   1,234,748 99.7 3,719 0.3   1,221,802 98.7 16,665 1.4  
Type of health insurance
 Self-employed 1,689,352 97.3 46,924 2.7  < .0001 1,675,974 96.5 60,302 3.5  < .0001 1,729,256 99.6 7,020 0.4  < .0001 1,710,475 98.5 25,801 1.5  < .0001
 Employee 4,546,866 97.8 102,663 2.2   4,512,048 97 137,481 3   4,636,691 99.7 12,838 0.3   4,588,734 98.7 60,795 1.3  
 Medical aid 33,340 94.5 1,946 5.5   32,979 93.5 2,307 6.5   35,060 99.4 226 0.6   34,430 97.6 856 2.4  
Residential area
 Seoul 1,281,035 97.7 29,985 2.3  < .0001 1,271,383 97 39,637 3  < .0001 1,307,052 99.7 3,968 0.3  < .0001 1,295,457 98.8 15,563 1.2  < .0001
 Metropolitan region 1,544,941 97.6 37,502 2.4   1,533,021 96.9 49,422 3.1   1,576,887 99.7 5,556 0.4   1,557,354 98.4 25,089 1.6  
 Small cities 3,027,116 97.7 72,423 2.3   3,003,602 96.9 95,937 3.1   3,090,716 99.7 8,823 0.3   3,059,769 98.7 39,770 1.3  
 Rural 416,466 97.3 11,623 2.7   412,995 96.5 15,094 3.5   426,352 99.6 1,737 0.4   421,059 98.4 7,030 1.6  
Mode of delivery
 Vaginal delivery 2,170,826 98.8 27,032 1.2  < .0001 2,155,660 98.1 42,198 1.9  < .0001 2,194,396 99.8 3,462 0.2  < .0001 2,177,073 99.1 20,785 1  < .0001
 Instrument delivery 1,750,562 98 35,350 2   1,736,117 97.2 49,795 2.8   1,782,129 99.8 3,783 0.2   1,758,974 98.5 26,938 1.5  
 Cesarean section 2,348,170 96.3 89,151 3.7   2,329,224 95.6 108,097 4.4   2,424,482 99.5 12,839 0.5   2,397,592 98.4 39,729 1.6  
Preterm birth
 No 6,139,508 97.8 138,641 2.2  < .0001 6,092,686 97.1 185,463 3  < .0001 6,259,755 99.7 18,394 0.3  < .0001 6,196,081 98.7 82,068 1.3  < .0001
 Yes 130,050 91 12,892 9   128,315 89.8 14,627 10.2   141,252 98.8 1,690 1.2   137,558 96.2 5,384 3.8  
Parity
 0 3,248,026 97.4 86,637 2.6  < .0001 3,219,016 96.5 115,647 3.5  < .0001 3,323,886 99.7 10,777 0.3  < .0001 3,283,131 98.5 51,532 1.6  < .0001
 1 +  3,021,532 97.9 64,896 2.1   3,001,985 97.3 84,443 2.7   3,077,121 99.7 9,307 0.3   3,050,508 98.8 35,920 1.2  
Multiple birth
 No 6,186,857 97.8 141,715 2.2  < .0001 6,139,428 97 189,144 3  < .0001 6,309,615 99.7 18,957 0.3  < .0001 6,244,363 98.7 84,209 1.3  < .0001
 Yes 82,701 89.4 9,818 10.6   81,573 88.2 10,946 11.8   91,392 98.8 1,127 1.2   89,276 96.5 3,243 3.5  
Prenatal care*
 Adequate 5,309,789 97.8 122,423 2.3  < .0001 5,267,814 97 164,398 3  < .0001 5,416,867 99.7 15,345 0.3  < .0001 5,358,203 98.6 74,009 1.4  < .0001
 Intermediate 871,738 97.1 25,838 2.9   865,763 96.5 31,813 3.5   893,375 99.5 4,201 0.5   885,419 98.7 12,157 1.4  
 Inadequate 57,314 96.6 2,006 3.4   56,861 95.9 2,459 4.2   58,990 99.4 330 0.6   58,436 98.5 884 1.5  
 Missing 31,983      31,983      31,983      31,983     
Maternal comorbidities
 0 3,908,136 98.2 73,223 1.8  < .0001 3,880,064 97.5 101,295 2.5  < .0001 3,972,890 99.8 8,469 0.2  < .0001 3,935,912 98.9 45,447 1.1  < .0001
 1 +  2,361,422 96.8 78,310 3.2   2,340,937 96 98,795 4.1   2,428,117 99.5 11,615 0.5   2,397,727 98.3 42,005 1.7  
Type of hospital
 ≥ 500 beds 341,950 89.8 38,680 10.2  < .0001 337,394 88.6 43,236 11.4  < .0001 376,134 98.8 4,496 1.2  < .0001 366,186 96.2 14,444 3.8  < .0001
 100–499 beds 669,389 95.2 33,786 4.8   661,773 94.1 41,402 5.9   697,438 99.2 5,737 0.8   690,670 98.2 12,505 1.8  
 30–99 beds 2,513,725 98.5 37,579 1.5   2,496,628 97.9 54,676 2.1   2,545,664 99.8 5,640 0.2   2,518,029 98.7 33,275 1.3  
 < 30 beds 2,744,494 98.5 41,488 1.5   2,725,206 97.8 60,776 2.2   2,781,771 99.9 4,211 0.2   2,758,754 99 27,228 1  
Region of hospital
 Seoul 1,294,441 97.3 35,505 2.7  < .0001 1,284,473 96.6 45,473 3.4  < .0001 1,325,181 99.6 4,765 0.4  < .0001 1,312,693 98.7 17,253 1.3  < .0001
 Metropolitans 1,747,196 97.5 45,328 2.5   1,733,515 96.7 59,009 3.3   1,785,397 99.6 7,127 0.4   1,761,969 98.3 30,555 1.7  
 Small cities 3,174,813 97.9 69,582 2.1   3,150,354 97.1 94,041 2.9   3,236,279 99.8 8,116 0.3   3,205,299 98.8 39,096 1.2  
 Rural 53,108 97.9 1,118 2.1   52,659 97.1 1,567 2.9   54,150 99.9 76 0.1   53,678 99 548 1  
Total 6,269,558 97.6 151,533 2.4   6,221,001 96.9 200,090 3.1   6,401,007 99.7 20,084 0.3   6,333,639 98.6 87,452 1.4  
  1. *Prenatal care is estimated using Kessner’s adequate prenatal care index
  2. Maternal comorbidities included are: cardiac disease, renal disease, musculoskeletal disease, digestive disorder, blood disease, mental disorders, CNS disease, rheumatic heart disease, placentation disorder, chronic hypertension, pregnancy hypertension, lupus, collagen vascular disorder, rheumatoid arthritis, diabetes, diabetes complicating pregnancy, obesity, and asthma/chronic bronchitis
  3. EURONET-SAMM European Network on Severe Acute Maternal Morbidity, SAMM severe acute maternal morbidity, SMM severe maternal morbidity, US-CDC United States Centers for Disease Control and Prevention
  4. aExcluding hospital length of stay