Comparison of basic characteristics between the HELIX entire cohort (n=31 472), the subcohort (n=1301) and the child panel study (n=157)
| Entire cohort | Subcohort | Panel study* | |
| (n=31 472) | (n=1301) | (n=157) | |
| Child characteristics | |||
| Sex (%) | |||
| Male | 51.2 | 54.7† | 56.1 |
| Female | 48.8 | 45.4† | 43.9 |
| Birth weight, g (SD) | 3372 (547) | 3379 (508) | 3346 (479) |
| Gestational age, weeks (SD) | 39.7 (1.8) | 39.6 (1.7) | 39.5 (1.6) |
| Family characteristics | |||
| Maternal age, years (SD) | 29.6 (5.2) | 30.8 (4.9)† | 31.0 (4.9)‡ |
| Maternal education (%) | |||
| Low | 22.7 | 6.8† | 6.8 |
| Middle | 25.7 | 34.5† | 34.5 |
| High | 51.6 | 51.8† | 51.8 |
| Maternal BMI* (%) | |||
| Underweight/normal weight | 58.6 | 60.9 | 58.1 |
| Overweight | 25.6 | 24.4 | 25.8 |
| Obesity | 15.8 | 14.7 | 16.1 |
| Country of origin of parents (%) | |||
| Both from other country | 21 | 11.1† | 5.2‡ |
| One parent from other country | 6.3 | 7.5† | 4.5‡ |
| Both parents from country of cohort | 65.7 | 81.4† | 90.3‡ |
| Parity (%) | |||
| 0 previous pregnancies | 50.7 | 45.9† | 42.4 |
| ≥1 previous pregnancies | 49.3 | 54.1† | 57.6 |
| Maternal smoking during pregnancy (%) | |||
| No | 87.9 | 83.1† | 85.3 |
| Yes | 12.1 | 14.8† | 14.7 |
*BMI grouped according to WHO categories for underweight (<18.5 kg/m2), normal (18.5–24.9 kg/m2), overweight (25–29.9 kg/m2) and obese (≥30 kg/m2).
†P<0.05 comparing the subcohort (n=1301) with the entire cohort.
‡P<0.10 comparing the child panel study with non-panel subcohort children in the same cohorts (excluding MoBa).
HELIX, Human Early Life Exposome; MoBa, Norwegian Mother and Child Cohort Study.