Characteristics of lead sample, compared to the rest of ALSPAC cohort
| Lead sample,n (%) | Rest of ALSPAC, n (%) | p Value | |
| Gender | |||
| Boy | 276 (56.6) | 7047 (51.5) | 0.030 |
| Girl | 212 (43.4) | 6624 (48.5) | |
| Maternal education | |||
| None/CSE | 54 (11.1) | 2468 (20.6) | 0.000 |
| Vocational | 53 (10.9) | 1178 (9.8) | |
| O level | 175 (35.9) | 4155 (34.6) | |
| A level | 137 (28.1) | 2666 (22.2) | |
| Degree | 69 (14.1) | 1538 (12.8) | |
| Paternal social class | |||
| I | 62 (12.7) | 1143 (10.9) | 0.242 |
| II | 170 (34.8) | 3583 (34.0) | |
| III non-manual | 62 (12.7) | 1137 (10.8) | |
| III manual | 136 (27.9) | 3334 (31.7) | |
| IV and V | 58 (11.9) | 1336 (12.7) | |
| Housing | |||
| Mortgaged/owned | 408 (83.6) | 9474 (73.0) | 0.000 |
| Rented/other | 80 (16.4) | 3496 (27.0) | |
| Maternal smoking in pregnancy | |||
| No | 412 (84.4) | 9564 (74.5) | 0.000 |
| Yes | 76 (15.6) | 3273 (25.5) |
ALSPAC, Avon Longitudinal Study of Parents and Children; CSE, Certificate of Secondary Education; O level, Ordinary level General Certificate of Education; A level, Advanced level General Certificate of Education.