Characteristics of children who were and were not seen at age 3 years
| Parental characteristics | Children seen at 3 years (n=1548) | Children not seen at 3 years (n=320) | p Value |
| Mean (SD) mother's age at child's birth (years) | 30.2 (3.8) | 29.4 (3.8) | 0.001 |
| Mother's education A level or above, n (%) | 900 (57%) | 150 (47%) | <0.001 |
| Maternal smoking during pregnancy, n (%) | 245 (16%) | 80 (27%) | <0.001 |
| Maternal asthma, n (%) | 344 (22%) | 74 (24%) | 0.599 |
| Maternal eczema in childhood, n (%) | 275 (18%) | 50 (16%) | 0.432 |
| Maternal rhinitis, n (%) | 639 (42%) | 118 (38%) | 0.225 |
| Paternal asthma, n (%) | 264 (17%) | 60 (20%) | 0.567 |
| Paternal eczema in childhood, n (%) | 156 (11%) | 31 (10%) | 0.897 |
| Paternal rhinitis, n (%) | 506 (34%) | 102 (34%) | 0.883 |
| Birth characteristics | |||
| Mean (SD) birth weight (g) | 3525 (475) | 3456 (467) | 0.020 |
| Mean (SD) gestational age (weeks) | 40.1 (1.2) | 40.1 (1.2) | 0.909 |
| Primiparous, n (%) | 704 (46%) | 114 (36%) | 0.001 |
| Attempted breastfeeding, n (%)* | 1269 (83%) | 162 (70%) | <0.001 |
| Characteristics at 6-month follow-up* | |||
| Maternal smoking, n (%) | 284 (18%) | 73 (30%) | <0.001 |
| Other smokers in the home, n (%) | 461 (31%) | 86 (35%) | 0.145 |
| Ever wheezed, n (%) | 402 (26%) | 83 (34%) | 0.013 |
| Cat or dog in home, n (%) | 699 (45%) | 105 (43%) | 0.384 |
| Characteristics at 1-year follow-up* | |||
| Wheezed in past 6 months, n (%) | 464 (30%) | 80 (41%) | 0.002 |
| Cat or dog in home, n (%) | 675 (44%) | 82 (42%) | 0.575 |
| Characteristics at 2-year follow-up* | |||
| Wheezed in past year, n (%) | 414 (27%) | 28 (27%) | 0.954 |
↵* Of the 320 children not seen at 3 years, 247 were seen at 6 months, 196 at 1 year and 104 at 2 years.