Characteristics of the study cohort based on self-reported and breath carbon monoxide confirmed smoking status at the first antenatal visit
| Characteristic | Total (n=250) | Non-smokers (n=187) | Verified smokers* (n=63) | P values |
| Age (mean, SD) (years) | 31.0 (5.3) | 31.8 (5.1) | 28.4 (5.2) | <0.001 |
| BMI (mean, SD) (kg/m2) | 26.4 (6.1) | 26.3 (5.4) | 27.0 (7.8) | 0.481 |
| Obese (%) | 19.3 | 17.0 | 26.2 | 0.078 |
| Nationality (%) | ||||
| Ireland | 76.8 | 75.1 | 82.0 | 0.106 |
| EU 14 | 4.8 | 3.7 | 8.2 | 0.089 |
| EU 13 | 8.4 | 10.1 | 3.3 | - |
| Other | 10.0 | 11.1 | 6.6 | – |
| Occupation (%)† | ||||
| Professional/managerial | 25.8 | 32.1 | 6.7 | – |
| Skilled manual/non-manual | 29.9 | 32.1 | 23.3 | 0.079 |
| Semi-manual/unskilled manual | 16.8 | 13.6 | 26.7 | <0.001 |
| Unemployed (%) | 27.5 | 22.3 | 43.3 | <0.001 |
| Married (%) | 52.0 | 61.4 | 23.0 | <0.001 |
| Years of continuous education (years) (mean, SD) | 16.0 (3.5) | 16.4 (3.5) | 14.5 (3.2) | <0.01 |
| Age completed education (years) (mean, SD) | 21.2 (4.2) | 21.8 (4.2) | 19.0 (3.1) | <0.001 |
| Nulliparas (%) | 34.8 | 32.8 | 41.0 | 0.106 |
| Planned pregnancy (%) | 65.6 | 72.0 | 45.9 | <0.001 |
| Daily passive smoke exposure (%) | 28.0 | 15.9 | 65.6 | <0.001 |
| Alcohol before pregnancy (%) | 32.9 | 68.3 | 63.5 | 0.259 |
| Alcohol during pregnancy (%) | 2.8 | 2.6 | 3.3 | – |
| Illicit drugs before pregnancy (%) | ||||
| Cannabis only | 7.6 | 5.8 | 13.1 | 0.038 |
| Other drugs | 6.8 | 5.3 | 11.5 | 0.058 |
| Illicit drugs during pregnancy (%) | ||||
| Cannabis only | 2.4 | 1.1 | 6.6 | – |
| Other drugs | 1.2 | 0.0 | 4.9 | – |
P values indicate significance between non-smokers and verified smokers.
*Women who self-report they are currently smoking and women who had a carbon monoxide level of ≥3 ppm.
†Missing data n=6.
BMI, Body Mass Index.
- The number of values for this variable was too small to statistically analyse