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Table 1 Characteristics of Project Viva mother–infant pairs with cord blood and mid-childhood samples

From: Prenatal metal exposure, cord blood DNA methylation and persistence in childhood: an epigenome-wide association study of 12 metals

  Cord blood (N = 361) Mid-childhood (N = 333)a
  N or median % or IQR N or median % or IQR
Maternal characteristics     
Age at enrollment (years), median (IQR) 32.4 (29.7, 35.9) 32.9 (29.7, 36.2)
College graduate 255 70.6% 234 70.3%
Smoking during pregnancy 41 11.4% 38 11.4%
Annual household income > $70,000 218 60.4% 206 61.9%
Nulliparous 177 49.0% 150 45.0%
Prenatal BMI, median (IQR) 23.5 (21.3, 27.2) 23.5 (21.5, 26.6)
Red blood cell concentration (ng/g), median (IQR)     
 As 0.86 (0.46, 1.5) 0.81 (0.44, 1.64)
 Ba 3.15 (2.06, 5.95) 3.10 (1.96, 5.57)
 Cd 0.39 (0.27, 0.56) 0.40 (0.27, 0.55)
 Cr 1.31 (0.86, 1.91) 1.37 (0.87, 2.16)
 Cs 2.53 (2.02, 3.14) 2.48 (1.94, 3.14)
 Cu 562 (517, 620) 560 (513.0, 619.0)
 Hgb 3.19 (1.69, 6.68) 3.26 (1.85. 5.89)
 Mg 41,500 (37,100, 46,400) 41,000 (36,600, 46,000)
 Mn 15.80 (13.10, 19.70) 15.70 (12.80, 19.80)
 Pb 18.10 (13.90, 23.80) 18.00 (14.00, 19.00)
 Se 249 (222, 279) 247 (222, 274)
 Zn 10,300 (9,380, 11,600) 10,300 (9,280, 11,500)
Infant characteristics     
Female 169 46.8% 158 47.4%
Gestational age (weeks), median (IQR) 40 (39.0, 40.9) 39.9 (38.9, 40.6)
Birth weight z-score 0.19 (− 0.35, 0.90) 0.24 (− 0.35, 0.97)
Race/ethnicity     
  White 254 70.4% 221 66.4%
  Black 41 11.4% 52 15.6%
  Hispanic 20 5.5% 17 5.1%
  Asian 8 2.2% 9 2.7%
  More than one race or other 38 10.5% 34 10.2%
Age at mid-childhood blood draw (years), median (IQR) 7.66 (7.38, 8.25)
  1. aA total of 189 mother–infant pairs had both cord blood and mid-childhood DNAm data
  2. bCord blood: N = 358; mid-childhood: N = 326; data are complete for all other variables