| Cord blood (N = 361) | Mid-childhood (N = 333)a | ||
---|---|---|---|---|
 | N or median | % or IQR | N or median | % or IQR |
Maternal characteristics | Â | Â | Â | Â |
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) | Â | Â | Â | Â |
 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 | Â | Â | Â | Â |
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 | Â | Â | Â | Â |
  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) |