Maternal characteristics and child birth weight by the grandmother's smoking when pregnant with the mother
| Characteristic | No (n=34 859) | Yes (n=12 253) | Don't know (n=4988) |
|---|---|---|---|
| Maternal age at delivery (mean (SD)) | 30.5 (4.4) | 30.1 (4.5) | 30.6 (4.5) |
| Maternal parity (%) | |||
| Primiparous | 49.1 | 45.0 | 46.7 |
| 1 | 33.4 | 36.0 | 35.1 |
| 2 | 13.7 | 15.0 | 14.6 |
| 3 or more | 3.8 | 4.1 | 3.6 |
| Maternal education (%) | |||
| Less than high school | 4.1 | 8.7 | 6.3 |
| High school | 23.9 | 32.9 | 30.2 |
| Up to 4 years of college | 44.4 | 40.4 | 41.4 |
| More than 4 years of college | 27.5 | 18.0 | 22.1 |
| Maternal yearly salary (%) | |||
| <200 000 NOK | 10.0 | 10.1 | 9.4 |
| 200 000–400 000 NOK | 54.7 | 57.5 | 57.3 |
| >400 000 NOK | 35.3 | 32.4 | 33.3 |
| Maternal pre-pregnancy BMI (%) | |||
| Underweight (<18.5) | 3.1 | 2.5 | 2.9 |
| Normal weight (18.5–24.9) | 69.2 | 60.3 | 64.0 |
| Overweight (25–29.9) | 20.2 | 25.0 | 23.2 |
| Obese (≥30) | 7.4 | 12.3 | 10.0 |
| Maternal asthma (%) | |||
| No | 93.4 | 91.5 | 91.9 |
| Yes | 6.6 | 8.5 | 8.1 |
| Maternal smoking during pregnancy (%) | |||
| No | 95.0 | 86.1 | 91.2 |
| Yes | 5.0 | 13.9 | 8.8 |
| Child birth weight, g (mean (SD)) | 3599 (534) | 3626 (555) | 3605 (540) |
Frequencies based on sample used for current asthma at 36 months classified based on follow-up Norwegian Mother and Child Cohort Study (MoBa) questionnaire.
Missing covariate information <2% for each individual covariate.
Given the large sample size, all p values for χ2 tests (categorical covariates) and analysis of variance (continuous covariates) <0.01.