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Table 2 Preterm birth (PTB) rates according to maternal systemic/localized comorbidity and gestational age (weeks) at delivery, and the proportions of comorbidity among PTBs

From: Association between maternal comorbidity and preterm birth by severity and clinical subtype: retrospective cohort study

  All PTB % Medically indicated % PPROM* % Spontaneous % Comorbidity % Total births
  < 37    < 28 28-31 32-36 < 37    < 28 28-31 32-36 < 37    < 28 28-31 32-36 < 37 < 37  
Systemic comorbidity                
   Hypertension                
Preeclampsia/eclampsia 24.1    1.0 3.3 16.3 20.6    0 0.1 1.2 1.3    0 0.1 2.1 2.2 8.7 29,915
Pre-existing 11.0    0.2 0.7 5.8 6.7    0.1 0.1 1.9 2.1    0.1 0.1 1.9 2.1 0.8 7,439
Gestational 6.1    0.1 0.2 3.2 3.5    0 0.1 1.1 1.2    0 0 1.3 1.4 1.0 11,380
   Cardiovascular disease 10.3    0.2 0.6 4.4 5.3    0.2 0.3 2.1 2.6    0.2 0 2.2 2.5 0.6 4,434
   Diabetes                
Pre-existing 13.1    0.1 0.6 5.5 6.1    0.1 0.5 3.1 3.7    0.1 0.3 2.9 3.2 2.7 16,938
Gestational 8.4    0.1 0.2 2.6 2.8    0.1 0.2 2.4 2.7    0 0.1 2.8 2.9 5.1 50,313
   Edema/renal disease 17.0    0.6 1.9 9.9 12.4    0.1 0.2 1.6 2.0    0.3 0.1 2.3 2.6 0.8 3,977
   Genitourinary infection 8.4    0.2 0.5 2.7 3.3    0.2 0.4 2.0 2.6    0.2 0.1 2.1 2.5 3.2 31,477
   General infection 10.0    0.2 0.4 3.2 3.8    0.3 0.4 2.2 2.9    0.3 0.2 2.7 3.2 1.9 16,024
   Thyroid disease 8.9    0.2 0.4 3.0 3.7    0.2 0.3 2.3 2.8    0.2 0.2 2.2 2.5 1.4 12,687
   Anemia 6.9    0.2 0.4 2.3 2.9    0.2 0.2 1.5 2.0    0.2 0.1 1.7 2.0 11.7 140,410
   Drug dependence 21.4    0.2 0.8 4.5 5.5    0.6 0.7 5.0 6.2    0.6 0.7 8.5 9.8 3.9 3,229
   Mental disorders 13.2    0.4 0.5 3.7 4.5    0.3 0.6 3.2 4.1    0.4 0.3 3.9 4.6 9.3 7,688
Localized comorbidity                
   Hemorrhage                
Placental abruption 31.9    1.3 2.4 9.9 13.6    1.3 1.6 3.6 6.6    2.3 1.8 7.6 11.7 8.6 22,278
Placenta previa 35.2    0.8 2.9 26.3 30.0    0.9 0.5 2.4 3.8    0.3 0.2 1.1 1.5 2.3 5,265
   Chorioamnionitis 11.0    0.3 0.3 1.4 1.9    1.2 1.2 3.1 5.5    1.0 0.5 2.1 3.6 7.3 55,133
   Amniotic sac                
Polyhydramnios 12.5    0.3 0.8 4.9 6.0    0.2 0.3 2.0 2.5    0.3 0.5 3.4 4.1 1.3 8,861
Oligohydramnios 20.6    0.8 1.8 10.4 13.0    1.1 1.4 3.2 5.7    0.3 0.2 1.5 1.9 3.8 15,293
   Cervical incompetence 47.4    3.4 1.5 6.4 11.2    6.3 2.7 5.7 14.7    11.3 2.1 8.1 21.5 1.5 2,570
   Structural abnormality 13.0    0.6 1.1 5.1 6.7    0.4 0.6 3.2 4.2    0.4 0.2 1.5 2.1 3.1 19,515
   Previous cesarean delivery 5.8    0.1 0.2 2.9 3.3    0.1 0.1 1.3 1.5    0.1 0.1 0.9 1.0 8.4 118,608
   Fetal anomaly 43.2    8.2 1.9 11.7 21.9    0.2 0.6 2.4 3.2    12 0.6 5.5 18.1 0.5 935
Total 6.2    0.1 0.2 1.5 1.8    0.1 0.1 1.7 1.9    0.1 0.1 2.2 2.5   1,329,737
  1. * Preterm premature rupture of membranes
  2. † Spontaneous preterm labour before 37 weeks of gestation with intact membranes
  3. ‡ Proportion of comorbidity among PTBs overall