Table 1.
Descriptive characteristics of the study sample.
| GIPUZKOA | SABADELL | VALENCIA | p-Value * | TOTAL | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| N = 313 | N = 443 | N = 339 | N = 1095 | |||||||
| Variables | N (%) | Mean (SD) | N (%) | Mean (SD) | N (%) | Mean (SD) | N (%) | Mean (SD) | ||
| Child characteristics | ||||||||||
| Sex | Female | 157 (50.16) | 217 (48.98) | 166 (48.97) | 0.939 | 540 (49.32) | ||||
| Male | 156 (49.84) | 226 (51.02) | 173 (51.03) | 555 (50.68) | ||||||
| Missing | 0 (0) | 0 (0) | 0 (0) | 0 (0) | ||||||
| Preterm | No | 301 (96.17) | 425 (95.94) | 320 (94.4) | 0.168 | 1046 (95.53) | ||||
| Yes | 11 (3.51) | 12 (2.71) | 18 (5.31) | 41 (3.74) | ||||||
| Missing | 1 (0.32) | 6 (1.35) | 1 (0.29) | 8 (0.73) | ||||||
| Sibling order | Not first | 143 (45.69) | 188 (42.44) | 147 (43.36) | 0.669 | 478 (43.65) | ||||
| First | 170 (54.31) | 255 (57.56) | 192 (56.64) | 617 (56.35) | ||||||
| Missing | 0 (0) | 0 (0) | 0 (0) | 0 (0) | ||||||
| Lives with mother/father | Both | 295 (94.25) | 426 (96.16) | 332 (97.94) | 0.488 | 1053 (96.16) | ||||
| Only one | 3 (0.96) | 5 (1.13) | 7 (2.06) | 15 (1.37) | ||||||
| Missing | 15 (4.79) | 12 (2.71) | 0 (0) | 27 (2.47) | ||||||
| Number of people who they live with | Missing | 15 (4.79) | 2.58 (0.72) | 12 (2.71) | 2.57 (0.79) | 0 (0) | 2.58 (0.76) | 0.997 | 27 (2.47) | 2.57 (0.76) |
| Child’s age at the time of the test | Missing | 119 (1.74) | 4.41 (0.22) | 1 (0.09) | 4.44 (0.26) | 0 (0) | 5.92 (0.32) | <0.001 | 20 (1.83) | 4.90 (0.75) |
| Breastfeeding | Missing | 13 (4.15) | 29.33 (20.14) | 1 (0.23) | 27.48 (19.64) | 0 (0) | 23.04 (19.3) | <0.001 | 14 (1.28) | 26.6 (19.82) |
| Hg (μg/l) in umbilical cord | Missing | 35 (11.18) | 9.6 (5.83) | 117 (26.41) | 8.35 (6.53) | 95 (28.02) | 15.34 (11.6) | <0.001 | 247 (22.56) | 10.77 (8.65) |
| Maternal characteristics | ||||||||||
| Ferritin level (log scale) | Missing | 0 (0) | 3.28 (0.74) | 0 (0) | 3.25 (0.79) | 0 (0) | 3.45 (0.68) | <0.001 | 0 (0) | 3.32 (0.75) |
| Maternal blood collection week | Missing | 0 (0) | 13.33 (1.31) | 2 (0.45) | 13 (1.8) | 0 (0) | 8.09 (4.23) | <0.001 | 2 (0.18) | 11.57 (3.58) |
| Alcohol intake during pregnancy | Missing | 0 (0) | 0.19 (0.47) | 0 (0) | 0.37 (1.07) | 0 (0) | 0.41 (1.19) | 0.009 | 0 (0) | 0.33 (0.98) |
| Pre-pregnancy BMI | Missing | 0 (0) | 22.9 (3.35) | 0 (0) | 23.87 (4.71) | 0 (0) | 23.8 (4.43) | 0.004 | 0 (0) | 23.57 (4.29) |
| Age | Missing | 0 (0) | 31.58 (3.48) | 1 (0.23) | 30.66 (4.1) | 0 (0) | 30.64 (4.06) | 0.002 | 1 (0.09) | 30.92 (3.94) |
| Mental health (14 months after birth) | Missing | 39 (12.46) | 9.23 (3.33) | 27 (6.09) | 9.9 (3.95) | 339 (100) | − | 0.021 | 405 (36.99) | 9.64 (3.72) |
| Parity | Missing | 0 (0) | 0.53 (0.64) | 2 (0.45) | 0.49 (0.65) | 0 (0) | 0.5 (0.64) | 0.705 | 2 (0.18) | 0.51 (0.64) |
| Smoking during pregnancy | No | 269 (85.94) | 379 (85.55) | 264 (77.88) | <0.001 | 912 (83.29) | ||||
| Yes | 34 (10.86) | 58 (13.09) | 75 (22.12) | 167 (15.25) | ||||||
| Missing | 10 (3.19) | 6 (1.35) | 0 (0) | 16 (1.46) | ||||||
| Country of birth | Spain | 305 (97.44) | 402 (90.74) | 318 (93.81) | 0.001 | 1025 (93.61) | ||||
| Other | 8 (2.56) | 39 (8.8) | 21 (6.19) | 68 (6.21) | ||||||
| Missing | 0 (0) | 2 (0.45) | 0 (0) | 2 (0.18) | ||||||
| Social class | No manual | 190 (60.7) | 247 (55.76) | 157 (46.31) | <0.001 | 594 (54.25) | ||||
| Manual | 123 (39.3) | 196 (44.24) | 182 (53.69) | 501 (45.75) | ||||||
| Missing | 0 (0) | 0 (0) | 0 (0) | 0 (0) | ||||||
| Education level | Primary | 34 (10.86) | 104 (3.48) | 90 (26.55) | <0.001 | 228 (20.82) | ||||
| Secondary | 116 (37.06) | 190 (42.89) | 155 (45.72) | 461 (42.1) | ||||||
| University | 162 (51.76) | 146 (32.96) | 94 (27.73) | 402 (36.71) | ||||||
| Missing | 1 (0.32) | 3 (0.68) | 0 (0) | 4 (0.37) | ||||||
* One-way ANOVA for mean differences and chi-squared test for categorical variables.