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Table 2 Maternal, pregnancy and perinatal characteristics associated with loss to follow-up and the presence or absence of neurodevelopmental impairment at 2 years of corrected age (N = 1737)

From: Strategies for assessing the impact of loss to follow-up on estimates of neurodevelopmental impairment in a very preterm cohort at 2 years of age

  Responded to follow-up questionnaire Presence of moderate to severe neurodevelopmental impairment
Yes (n = 941, 54.2%) No (n = 796, 45.8%) p-value No (n = 683, 81.6%) Yes (n = 154, 18.4%) p-value
n (%) n (%) n (%) n (%)
Maternal characteristics
 Maternal age
  ≤ 24y 138 (14.8%) 256 (32.2%) < 0.001 93 (13.7%) 28 (18.3%) 0.35
  25y-34y 545 (58.3%) 397 (49.9%)   399 (58.7%) 85 (55.6%)  
  ≥ 35y 252 (27.0%) 142 (17.9%)   188 (27.6%) 40 (26.1%)  
  Missing 6 (0.6%) 1 (0.1%)   3 (0.4%) 1 (0.6%)  
 Foreign born/Ethnicity 121 (13.0%) 183 (23.2%) < 0.001 76 (11.2%) 20 (13.2%) 0.54
  Missing 8 (0.9%) 8 (1.0%)   6 (0.9%) 2 (1.3%)  
 Multiple pregnancy 285 (30.3%) 185 (23.3%) < 0.001 215 (31.5%) 37 (24.0%) 0.09
 Parity
  First child 580 (61.8%) 367 (46.2%) < 0.001 442 (64.8%) 86 (55.8%) 0.03
  Second child 225 (24.0%) 211 (26.6%)   159 (23.3%) 37 (24.0%)  
  Third or more 134 (14.3%) 216 (27.2%)   81 (11.9%) 31 (20.1%)  
  Missing 2 (0.2%) 2 (0.3%)   1 (0.1%) 0 (0.0%)  
 Previous cesarean section 90 (9.8%) 99 (13.1%) 0.03 63 (9.4%) 12 (8.1%) 0.62
  Missing 22 (2.3%) 40 (5.0%)   16 (2.3%) 5 (3.2%)  
 PPROM 203 (22.1%) 206 (27.2%) 0.01 145 (21.8%) 37 (24.3%) 0.60
  Missing 22 (2.3%) 40 (5.0%)   17 (2.5%) 2 (1.3%)  
 Antepartum hemorrhage after ≥20 weeks GA 205 (22.2%) 205 (27.0%) 0.31 139 (20.8%) 39 (25.7%) 0.19
  Missing 19 (2.0%) 36 (4.5%)   15 (2.2%) 2 (1.3%)  
 Delivery in level III 657 (70.0%) 530 (66.7%) 0.11 480 (70.5%) 110 (71.4%) 0.45
  Missing 2 (0.2%) 1 (0.1%)   2 (0.3%) 0 (0.0%)  
 Breastfeeding at discharge 649 (69.2%) 427 (53.8%) < 0.001 486 (71.5%) 97 (63.0%) 0.04
  Missing 3 (0.3%) 3 (0.4%)   3 (0.4%) 0 (0.0%)  
Neonatal characteristics
 Male 529 (56.2%) 426 (53.6%) 0.34 370 (54.2%) 108 (70.1%) < 0.001
  Missing 0 (0.0%) 1 (0.1%)    
 Gestational age at birth
  23wk-25wk 70 (7.4%) 64 (8.0%) 0.49 36 (5.3%) 24 (15.6%) < 0.001
  26wk-27wk 166 (17.6%) 109 (13.7%)   119 (17.4%) 27 (17.5%)  
  28wk-29wk 249 (26.5%) 228 (28.6%)   174 (25.5%) 50 (32.5%)  
  30wk-31wk 456 (48.5%) 395 (49.6%)   354 (51.8%) 53 (34.4%)  
 Small for gestational agea
  < 3th percentile 198 (21.0%) 153 (19.2%) 0.80 138 (20.2%) 42 (27.3%) 0.12
  3-10th percentile 111 (11.8%) 97 (12.2%)   85 (12.4%) 18 (11.7%)  
   > 10th percentile 632 (67.2%) 545 (68.6%)   460 (67.3%) 94 (61.0%)  
 Apgar score < 7 (5 min) 109 (11.8%) 117 (15.0%) 0.18 67 (10.0%) 30 (19.7%) < 0.001
  Missing 21 (2.2%) 17 (2.1%)   16 (2.3%) 2 (1.3%)  
 Surfactant 570 (60.6%) 458 (57.5%) 0.02 393 (57.5%) 111 (72.1%) < 0.001
 Any CPAPb 810 (86.1%) 649 (81.5%) 0.13 586 (85.8%) 136 (88.3%) 0.35
 Mechanical ventilation 551 (58.6%) 456 (57.3%) 0.07 372 (54.5%) 115 (74.7%) < 0.001
 Bronchopulmonary dysplasiac 175 (18.8%) 156 (20.0%) 0.59 111 (16.4%) 45 (29.2%) < 0.001
  Missing 9 (1.0%) 15 (1.9%)   7 (1.0%) 0 (0.0%)  
 Any severe morbidity 111 (11.8%) 90 (11.4%) 0.70 61 (8.9%) 38 (24.7%) < 0.001
  Missing 2 (0.2%) 9 (1.1%)   0 (0.0%) 0 (0.0%)  
 Any congenital anomalyd 46 (4.9%) 40 (5.0%) 0.75 29 (4.2%) 12 (7.8%) 0.06
 Any Surgery 75 (8.0%) 69 (8.7%) 0.83 39 (5.7%) 27 (17.5%) < 0.001
 Socioeconomic status
  1 (least deprivated) 236 (25.1%) 107 (13.4%) < 0.001 182 (26.7%) 36 (23.4%) 0.54
  2 193 (20.5%) 115 (14.5%)   146 (21.4%) 27 (17.5%)  
  3 194 (20.6%) 144 (18.1%)   142 (20.8%) 31 (20.1%)  
  4 149 (15.8%) 173 (21.7%)   102 (14.9%) 28 (18.2%)  
  5 (most deprivated) 140 (14.9) 213 (26.8%)   95 (13.9%) 26 (16.9%)  
  Missing 29 (3.1) 44 (5.5%)   16 (2.3%) 6 (3.9%)  
  1. P-value was adjusted on region of birth and doesn’t include missing category; aUsing intrauterine curves; bContinuous positive airway pressure; cOxygen dependency or assisted ventilation at 36 weeks post menstrual age; dCongenital anomalies reported to Eurocat