| Variable | MAAS | BAMSE | PIAMA | GINI/LISA South | GINI/LISA North |
| Females | 543/1185 (45.8) | 2024/4089 (49.5) | 1908/3963 (48.1) | 2054/4286 (47.9) | 1458/2989 (48.8) |
| Native ethnicity | 1059/1185 (95.0) | 2691/3398 (79.2) | 3485/3700 (94.2) | ||
| High socioeconomic status | 204/1078 (18.9) | 1574/3982 (39.5) | 1908/3812 (50.1) | 3224/4376 (73.7) | 1112/3291 (33.8) |
| Older siblings | 561/1073 (52.3) | 1980/4088 (48.4) | 1994/3937 (50.6) | 1454/3386 (42.9) | 1810/3363 (53.8) |
| Allergic mother | 683/1147 (59.5) | 651/4032 (16.2) | 1237/3963 (31.2) | 1914/4389 (43.6) | 1076/3376 (31.9) |
| Allergic father | 717/1138 (63.0) | 665/4032 (16.5) | 1217/3957 (30.8) | 1665/4316 (38.6) | 819/3333 (24.6) |
| ≥12 weeks of breastfeeding | 502/1115 (45.0) | 3657/3879 (94.3) | 1892/3896 (48.6) | 1463/3536 (41.4) | 1362/2713 (50.2) |
| Mother smoking during pregnancy | 119/1025 (11.6) | 527/4088 (12.9) | 696/3904 (17.8) | 527/3720 (14.2) | 497/2816 (17.6) |
| Any smoker living in the home | 438/1024 (42.8) | 855/4067 (21.0) | 1129/3935 (28.7) | 518/2598 (19.9) | 843/2786 (30.3) |
| Use of natural gas for cooking | 801/1028 (77.9) | 471/4089 (11.5) | 3236/3911 (82.7) | 282/3644 (7.7) | 123/2758 (4.5) |
| Visible signs of mould or damp in home | 177/1030 (17.2) | 1034/4077 (25.4) | 1047/3702 (28.3) | 667/2978 (22.4) | 542/2760 (19.6) |
| Dog(s) in home | 174/1028 (16.9) | 221/4089 (5.4) | 633/3935 (16.1) | 130/3555 (3.7) | 336/2686 (12.5) |
| Cat(s) in home | 205/1027 (20.0) | 405/4089 (9.9) | 1293/3940 (32.8) | 232/3555 (6.5) | 194/2686 (7.2) |
| Day care centre attendance# | 741/1087 (68.2) | 3205/3841 (83.4) | 1034/3703 (27.9) | 1019/3355 (30.4) | 43/2402 (1.8) |
| Hospitalised for respiratory infection# | 109/1185 (9.2) | 80/3535 (2.3) | 12/1465 (0.8) | 3/308 (1.0) | |
| Study subgroup | |||||
| Observational cohort | 1052/1185 (87.8) | 3182/3941 (80.7) | 1784/2949 (60.5) | 1955/3042 (64.3) | |
| Intervention group | 133/1185 (11.2) | 759/3941 (19.3) | 1165/2949 (39.5) | 1087/3042 (35.7) | |
| Birth weight g | 3462±510 (n=1132) | 3530±558 (n=4044) | 3507±546.1 (n=3914) | 3419±437 (n=3676) | 3531±475.6 (n=2772) |
| Gestational age weeks | 39.9±1.6 (n=1072) | 39.8±2.0 (n=4089) | 39.8±1.67 (n=3930) | 39.9±1.2 (n=1445) | 39.7±1.2 (n=346) |
| Maternal age at birth years | 30.4±4.8 (n=1115) | 30.7±4.5 (n=4088) | 30.3±3.90 (n=3920) | 31.4±4.5 (n=4401) | 30.1±4.2 (n=3387) |
Data are presented as n/N (%) or mean±sd. MAAS: Manchester Asthma and Allergy Study; BAMSE: Barn Allergi Miliö Stockholm Epidemiologi; PIAMA: Prevention and Incidence of Asthma and Mite Allergy; GINI: German Infant Nutritional Intervention; LISA: Lifestyle-Related Factors on the Development of the Immune System and Allergic Disease. #: during the first 2 years of life.