Table 1

Characteristics of the study cohort based on self-reported and breath carbon monoxide confirmed smoking status at the first antenatal visit

Verified smokers*
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 (%)19.317.026.20.078
Nationality (%)
 EU 138.410.13.3-
Occupation (%)†
 Skilled manual/non-manual29.932.123.30.079
 Semi-manual/unskilled manual16.813.626.7<0.001
 Unemployed (%)27.522.343.3<0.001
Married (%)52.061.423.0<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 (%)34.832.841.00.106
Planned pregnancy (%)65.672.045.9<0.001
Daily passive smoke exposure (%)28.015.965.6<0.001
Alcohol before pregnancy (%)32.968.363.50.259
Alcohol during pregnancy (%)
Illicit drugs before pregnancy (%)
 Cannabis only7.65.813.10.038
 Other drugs6.85.311.50.058
Illicit drugs during pregnancy (%)
 Cannabis only2.41.16.6
 Other drugs1.20.04.9
  • 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