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Table 1 Baseline characteristics of mothers and infants by hemoglobin (Hb) levels in the second trimester in this study

From: High hemoglobin level is a risk factor for maternal and fetal outcomes of pregnancy in Chinese women: A retrospective cohort study

  Total Hb levels (g/L) P value
< 110 110–119 120–129 > 130
No. of maternal cases 1911 405 779 583 144  
Maternal age (years) 31.0 (29.0, 34.0) 31.0 (28.5, 35.0) 31.0 (29.0, 34.0) 31.0 (29.0, 34.0) 31.0 (29.0, 35.0) 0.874
Age categories       0.278
  < 35 1445 (75.6) 297 (73.3) 592 (76.0) 451 (77.4) 105 (72.9)  
  ≥ 35 466 (24.4) 108 (26.7) 187 (24.0) 132 (22.6) 39 (27.1)  
BMI (kg/m2)   20.0 (18.4, 21.5) 20.5 (18.9, 21.9) 20.7 (19.1, 22.6) 21.7 (19.7, 23.6) < 0.001
Education       0.493
 Primary 78 (4.1) 20 (4.9) 27 (3.5) 24 (4.1) 7 (4.9)  
 Secondary 285 (14.9) 68 (16.8) 122 (15.7) 78 (13.4) 17 (11.8)  
 College or above 1548 (81.0) 317 (78.3) 630 (80.9) 481 (82.5) 120 (83.3)  
Conception method       0.015
 Natural 1869 (97.8) 383 (94.6) 768 (98.6) 576 (98.8) 142 (98.6)  
 Artificial 26 (1.4) 12 (3.0) 7 (0.9) 5 (0.9) 2 (1.2)  
Parity       0.113
 Nulliparity 815 (42.6) 180 (44.4) 314 (40.3) 257 (44.1) 64 (44.4)  
 Multipara 1096 (57.4) 225 (55.5) 465 (59.7) 326 (55.9) 80 (55.6)  
History of miscarriage 819 (42.9) 173 (42.7) 340 (43.6) 242 (41.5) 80 (55.6) 0.854
GDM 372 (19.5) 59 (14.6) 154 (19.8) 126 (21.6) 33 (22.9) 0.029
Hemoglobin (g/L)
 2nd trimester 117.0 (111.0, 123.0) 106.0 (102.0, 108.0) 115.0 (112.5, 117.3) 123.5 (121.5, 126.0) 133.0 (131.0, 135.0) < 0.001
 3rd trimester 118 (111.3, 124.3) 110.3 (105.3, 116.0) 117.5 (111.7, 122.5) 122.5 (116.3, 127.3) 128.2 (119.0, 134.5) < 0.001
Adverse maternal and fetal outcomes
 PTB 108 (5.7) 23 (5.7) 44 (5.6) 31 (5.3) 10 (6.9) 0.902
 LBW 66 (3.5) 15 (3.7) 21 (2.7) 21 (3.6) 9 (6.3) 0.184
 SGA 86 (4.5) 24 (5.9) 31 (4.0) 24 (4.1) 7 (4.9) 0.449
  1. Data are presented as the median (quartiles) for continuous variables and as n (%) for categorical variables
  2. Abbreviations: BMI body mass index, GDM gestational diabetes mellitus, LBW low-birth-weight infants, PTB preterm birth, SGA small-for-gestational-age infants