| All | 100 (2917) | 91.5 (2670) | 8.5 (247) |
| Gender | | | |
| Girls | 48.8 (1425) | 49.4 (1318) | 43.3 (107) |
| Birth weight | | | |
| <2500 g | 2.8 (80) | 2.0 (53) | 10.9 (27) |
| 2500–4500 g | 93.7 (2734) | 94.8 (2531) | 82.2 (203) |
| >4500 g | 3.5 (103) | 3.2 (86) | 6.9 (17) |
| Gestational age (weeks) | | | |
| <32 | 0.3 (8) | 0.1 (3) | 2.0 (5) |
| 32–36 | 4.1 (118) | 3.8 (100) | 7.3 (18) |
| 37–41 | 74.2 (2164) | 75.2 (2006) | 64.0 (158) |
| >41 | 21.4 (625) | 20.9 (559) | 26.7 (66) |
| Intrauterine growth restriction | | | |
| <10th percentile | 0.9 (27) | 0.6 (16) | 4.4 (11) |
| Number of respiratory infections in the first year | | | |
| 0 | 49.2 (1426) | 49.2 (1304) | 49.4 (122) |
| 1–2 | 37.4 (1084) | 37.4 (990) | 38.1 (94) |
| ⩾3 | 13.4 (386) | 13.4 (355) | 12.5 (31) |
| Maternal education | | | |
| Low | 20.7 (605) | 20.3 (542) | 25.5 (63) |
| Intermediate | 41.7 (1215) | 41.9 (1120) | 38.5 (95) |
| High | 37.6 (1097) | 37.7 (1008) | 36.0 (89) |
| Mother’s job | | | |
| Employed | 63.0 (1832) | 62.6 (1668) | 66.7 (164) |
| Self-employed | 4.8 (141) | 4.6 (122) | 7.7 (19) |
| Housewife | 26.8 (779) | 27.3 (727) | 21.1 (52) |
| Unemployed | 5.4 (157) | 5.5 (146) | 4.4 (11) |
| Maternal smoking during pregnancy | | | |
| Yes | 11.9 (348) | 12.0 (319) | 11.7 (29) |
| No of older siblings | | | |
| 0 | 50.0 (1455) | 48.8 (1273) | 73.7 (182) |
| 1 | 35.8 (1041) | 37.0 (984) | 23.1 (57) |
| ⩾2 | 14.2 (412) | 15.2 (404) | 3.2 (8) |
| Parents with allergy | | | |
| 0 | 51.3 (1495) | 51.4 (1371) | 50.2 (124) |
| 1 | 39.6 (1156) | 39.6 (1058) | 39.7 (98) |
| 2 | 9.1 (266) | 9.0 (241) | 10.1 (25) |