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Table 1 Characteristics of mothers and newborns according to different criteria of maternal ID

From: Iron deficiency in late pregnancy and its associations with birth outcomes in Chinese pregnant women: a retrospective cohort study

  Serum ferritin (< 12 μg/L) Serum transferrin (> 4 g/L) Transferrin/ferritin ratio log10 transform (> 5.52)
Deficient (N = 5995) Replete (N = 5574) Deficient (N = 6301) Replete (N = 5275) Deficient (N = 6233) Replete (N = 5331)
Maternal characteristics
 Maternal age at delivery (years) 28 (25–31)** 28 (26–31) 28 (25–31)** 28 (26–31) 28 (25–31)** 28 (26–32)
 ≤ 25 [N(%)] 1558 (25.99%)** 1168 (20.95%) 1577 (25.03%)** 1153 (21.86%) 1604 (25.73%)** 1122 (21.05%)
 26–29 [N(%)] 2461 (41.05%) 2401 (43.07%) 2633 (41.79%) 2227 (42.22%) 2576 (41.33%) 2282 (42.81%)
 ≥ 30 [N(%)] 1976 (32.96%)** 2005 (35.97%) 2091 (33.19%)** 1895 (35.92%) 2053 (32.94%)** 1927 (36.15%)
 BMI at delivery (kg/m2) 26.95 (25–29.30) 26.95 (24.98–29.38) 26.95 (24.97–29.30) 26.99 (25–29.36) 26.99 (25–29.30) 26.95 (24.97–29.36)
 < 25 [N(%)] 1461 (24.65%) 1399 (25.32%) 1600 (25.63%) 1262 (24.19%) 1512 (24.53%) 1347 (25.49%)
 ≥25 [N(%)] 4467 (75.35%) 4126 (74.68%) 4643 (74.37%) 3955 (75.81%) 4652 (75.47%) 3937 (74.51%)
Gravidity
 < 3 [N(%)] 4138 (69.02%)** 4086 (73.30%) 4403 (69.88%)** 3825 (72.51%) 4306 (69.08%)** 3914 (73.42%)
 ≥3 [N(%)] 1857 (30.98%)** 1488 (26.70%) 1898 (30.12%)** 1450 (27.49%) 1927 (30.92%)** 1417 (26.58%)
Parity
 No child [N(%)] 3309 (55.20%)** 3638 (65.27%) 3629 (57.59%)** 3321 (62.96%) 3454 (55.41%)** 3489 (65.45%)
 ≥1 child [N(%)] 2686 (44.80%)** 1936 (34.73%) 2672 (42.41%)** 1954 (37.04%) 2779 (44.59%)** 1842 (34.55%)
 Gestational age at delivery (week) 38.72 ± 1.62 38.66 ± 1.72 38.76 ± 1.54* 38.61 ± 1.81 38.73 ± 1.60 38.65 ± 1.74
 Systolic BP at delivery (mmHg) 120 (110–129)** 120 (110–130) 120 (110–129)** 120 (110–130) 120 (110–129)** 120 (110–130)
 Diastolic BP at delivery(mmHg) 72 (70–79)** 73 (70–80) 72 (70–80)** 73 (70–80) 72 (70–79)** 73 (70–80)
Delivery mode
 Vaginal delivery 3412 (56.91%) 2951 (52.94%) 3573 (56.71%) 3081 (58.41%) 3529 (56.62%) 3122 (58.56%)
 Cesarean section 2583 (43.09%) 2334 (41.87%) 2728 (43.29%) 2194 (41.59%) 2704 (43.38%) 2209 (41.44%)
 Inflammation (hsCRP > 5 mg/L) 1329 (22.17%)** 1639 (29.4%) 1465 (23.25%)** 1507 (28.57%) 1394 (22.36%)** 1572 (29.49%)
 Anemia (hemoglobin < 110 g/L) 2032 (33.89%)** 396 (7.1%) 1735 (27.54%)** 692 (13.12%) 2070 (33.21%)** 356 (6.85%)
 GDM 389 (6.49%)** 580 (10.41%) 539 (8.55%) 429 (8.13%) 429 (6.88%)** 539 (10.11%)
 ICP 301 (5.02%)** 415 (7.45%) 448 (7.11%)** 268 (5.08%) 333 (5.34%)** 383 (7.18%)
 PE 147 (2.45%)** 249 (4.47%) 190 (3.02%)* 208 (3.94%) 163 (2.62%)** 233 (4.37%)
 PIH 107 (1.78%)** 139 (2.49%) 133 (2.11%) 113 (2.14%) 114 (1.83%)** 132 (2.48%)
 PTB 383 (6.39%)* 411 (7.37%) 365 (5.79%)** 432 (8.19%) 389 (6.24%)** 404 (7.58%)
Newborn characteristics
 Sex
  Female 2829 (47.19%) 2623 (47.06%) 2984 (47.36%) 2473 (46.88%) 2985 (47.89%) 2465 (46.24%)
  Male 3166 (52.81%) 2951 (52.94%) 3317 (52.64%) 2802 (53.12%) 3248 (52.11%) 2866 (53.76%)
Birth length (cm) 49.88 ± 1.30** 49.74 ± 1.55 49.91 ± 1.22** 49.70 ± 1.64 49.89 ± 1.28** 49.72 ± 1.58
Birth weight (g) 3390 (3110–3680)** 3320 (3030–3610) 3380 (3100–3680)** 3320 (3020–3600) 3390 (3100–3680)** 3320 (3030–3600)
 < 2500 213 (3.55%)** 304 (5.45%) 209 (3.32%)** 310 (5.88%) 211 (3.39%)** 306 (5.74%)
 2500–4000 5276 (88.01%) 4923 (88.32%) 5544 (87.99%) 4660 (88.34%) 5484 (87.98%) 4710 (88.35%)
 > 4000 506 (8.44%)** 347 (6.23%) 548 (8.70%)** 305 (5.78%) 538 (8.63%)** 315 (5.91%)
Weight for gestational age
 SGA 428 (7.14%)** 595 (10.67%) 480 (7.62%)** 544 (10.31%) 440 (7.06%)** 583 (10.94%)
 AGA 4538 (75.70%) 4217 (75.65%) 4714 (74.81%) 4045 (76.68%) 4705 (75.49%) 4045 (75.88%)
 LGA 1029 (17.16%)** 762 (13.67%) 1107 (17.57%)** 686 (13.00%) 1088 (17.46%)** 703 (13.19%)
  1. Data were presented as median (IQR), mean ± SD and N (%) for continuous variables with normal distribution, continuous variables with skewed distribution, and categorical variables, respectively. *p < 0.05, **p < 0.01, according to Mann-Whitney test for skewed-distributed continuous variables, Student’s t-test for normally-distributed continuous variables, and Chi-square test for categorical variables
  2. Abbreviations: IQR interquartile range, SD standard deviation, BMI body mass index, BP blood pressure, hsCRP high sensitivity C-reactive protein, GDM gestational diabetes mellitus, ICP intrahepatic cholestasis of pregnancy, PE Preeclampsia, PIH pregnancy-induced hypertension, PTB pre-term birth, SGA/AGA/LGA small/appropriate/large for gestational age