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Table 1 Characteristics of included and excluded mother-child pairs

From: Prenatal plasma concentrations of Perfluoroalkyl and polyfluoroalkyl substances and neuropsychological development in children at four years of age

Characteristics Included (N = 533)
n (%) / Mean ± SD
Excluded (N = 692)
n (%) / Mean ± SD
P-value of Student’s t-test or Chi-square test
Maternal age at enrollment (years)
 Mean ± SD 27.9 ± 3.4 27.8 ± 3.4 0.7451
 < 25 81 (15.2) 103 (14.9) 0.7900
 25–30 299 (56.1) 404 (58.4)  
 ≥ 30 153 (28.7) 185 (26.7)  
Maternal pre-pregnancy BMI (kg/m2)
 Mean ± SD 20.6 ± 2.4 20.4 ± 2.4 0.1905
 < 18.5 98 (18.7) 146 (21.5) 0.2112
 18.5–24.9 395 (75.4) 506 (74.4)  
 ≥ 25 31 (5.9) 28 (4.1)  
Maternal education
 Blow high school 41 (7.7) 78 (11.3) 0.1064
 High School 76 (14.3) 99 (14.3)  
 College or above 415 (78.0) 514 (74.4)  
Paternal education
 Blow high school 28 (5.25) 57 (8.28) 0.9430
 High School 76 (14.26) 119 (17.3)  
 College or above 429 (80.49) 512 (74.42)  
Per capita household income (CNY)
 < 4000 113 (21.3) 140 (20.6) 0.0282
 4000–8000 212 (40.0) 277 (40.8)  
 > 8000 205 (38.7) 262 (38.6)  
Parity
 Nulliparous 459 (86.9) 569 (82.7) 0.0432
 Multiparous 69 (13.1) 119 (17.3)  
Maternal alcohol consumption during pregnancy
 No 454 (99.13) 508 (98.64) 0.4743
 Yes 4 (0.87) 7 (1.36)  
Maternal passive smoking before conception
 No 307 (57.8) 420 (60.9) 0.2811
 Yes 224 (42.2) 270 (39.1)  
Maternal prenatal depressive symptoms
 No 434 (81.43) 551 (79.62) 0.4309
 Yes 99 (18.57) 141 (20.38)  
Sex of child
 Boy 297 (55.7) 370 (53.7) 0.4816
 Girl 236 (44.3) 319 (46.3)  
Gestational age (weeks)
Mean ± SD 39.5 ± 1.3 39.51 ± 1.5 0.6182
 < 37 19 (3.6) 26 (3.8) 0.8640
 ≥ 37 513 (96.4) 666 (96.2)  
  1. Missing data: Included: pre-pregnancy BMI (n = 9), maternal education (n = 1), per capita household income (n = 3), parity (n = 5), maternal alcohol consumption during pregnancy (n = 75) and maternal passive smoking before conception (n = 2); Excluded: pre-pregnancy BMI (n = 12), maternal education (n = 1), paternal education (n = 4), per capita household income (n = 13), parity (n = 4), maternal alcohol consumption during pregnancy (n = 177), maternal passive smoking before conception (n = 2), and maternal prenatal depressive symptoms (n = 1)