Table 1. Characteristics of participants in the original cohort and the percentage analyzed (2004 Pelotas Birth Cohort; Pelotas, Brazil).
| Co-variables | Original cohort N (%) | Available information at 3 months of age N (%) | Available information at 12 months of age N (%) |
|---|---|---|---|
| Total | 4147 | 4011 | 3757 |
| Family monthly income (quintiles) | P=0.002 | P<0.001 | |
| 1 (poorest) | 846 (20.4) | 806 (20.1) | 709 (18.9) |
| 2 | 841 (20.3) | 803 (20.0) | 737 (19.6) |
| 3 | 802 (19.3) | 782 (19.5) | 745 (19.8) |
| 4 | 846 (20.4) | 829 (20.7) | 795 (21.2) |
| 5 (wealthiest) | 812 (19.6) | 791 (19.6) | 771 (20.5) |
| Schooling, years | P=0.006 | P<0.001 | |
| Up to 4 | 639 (15.6) | 608 (15.3) | 505 (13.6) |
| 5–8 | 1691 (41.2) | 1629 (41.0) | 1520 (40.8) |
| 9–11 | 1362 (33.2) | 1334 (33.6) | 1301 (34.9) |
| ⩾12 | 414 (10.1) | 402 (10.1) | 394 (10.6) |
| Maternal skin color | P=0.05 | P<0.001 | |
| White | 2528 (61.7) | 2459 (62.0) | 2340 (62.9) |
| Black | 675 (16.5) | 648 (16.3) | 584 (15.7) |
| Mulatto/Brown /Others | 896 (21.9) | 858 (21.6) | 796 (21.4) |
| Maternal age, years | P=0.59 | P=0.46 | |
| <20 | 792 (19.1) | 762 (19.0) | 713 (18.9) |
| 20–35 | 2919 (70.4) | 2825 (70.5) | 2656 (70.6) |
| >35 | 434 (10.5) | 422 (10.5) | 388 (9.4) |
| Primiparity | P=0.87 | P<0.001 | |
| Yes | 1644 (39.7) | 1591 (39.7) | 1541 (41.0) |
| No | 2502 (60.3) | 2419 (60.3) | 2215 (59.0) |
| Smoking (pregnancy) | P=0.01 | P<0.001 | |
| Yes | 1142 (27.5) | 1092 (27.2) | 995 (26.5) |
| No | 3005 (72.3) | 2919 (72.8) | 2762 (73.5) |
| Child's sex | P=0.36 | P=0.82 | |
| Boy | 2157 (52.0) | 2081 (51.9) | 1952 (52.0) |
| Girl | 1990 (48.0) | 1930 (48.1) | 1805 (48.0) |
P-value: χ2-test. Single birth participants.