Table 2

Median carbon monoxide levels and rates of breath carbon monoxide below and above cut-off by maternal characteristic

FactornCO ppm
(median, IQR)
CO <3 ppm (%)CO ≥3 ppm (%)P values
Occupation
 Professional/managerial†631.0 (1.0)93.76.3
 Skilled manual/non-manual731.0 (1.0)80.819.2<0.001
 Semi-manual/unskilled manual412.0 (3.5)**65.934.1<0.01
 Unemployed672.0 (5.0)*64.235.8<0.001
Marital status
 Married/civil partnership†1301.5 (1.0)90.010.0<0.001
 Single1202.0 (4.0)***63.336.7<0.001
Age (years)
 <30†962.0 (4.0)65.634.4<0.001
 ≥301541.0 (1.0)*84.415.6<0.001
Pregnancy Intention
 Planned†1641.0 (1.0)84.815.2<0.001
 Unplanned862.0 (4.0)**62.837.2<0.001
Age completed education
 <18 years352.0 (6.0)60.040.0<0.05
 ≥18 years†1461.0 (1.0)85.614.4<0.001
Years of continuous education
 <14 years681.0 (1.0)67.632.4<0.001
 >14 years†1141.0 (3.0)88.611.4<0.001
  • P values in final column indicate differences between CO ≤3 ppm and CO ≥3 ppm.

  • *0.05, **0.01, ***0.001; † , Reference group.

  • -   The number of values for this variable was too small to statistically analyse