Table 4 Associations between reduction in the absolute number of cigarettes smoked per day during pregnancy and socio-demographic characteristics of women (N = 4,774)

Maternal age (years)

  ≤ 19

1.16

0.93–1.45

0.180

1.14

1.01–1.28

0.035

 20–24

1.18

1.02–1.36

0.027

1.14

1.02–1.26

0.018

 25–29

1.00

1.00

 30–34

1.05

0.92–1.21

0.456

1.12

0.98–1.28

0.107

  ≥ 35

0.94

0.71–1.26

0.693

1.14

0.86–1.49

0.357

Residence

 Urban

1.00

1.00

 Rural

1.10

0.73–1.67

0.643

1.13

0.78–1.62

0.522

Ethnicity

 Russian

1.00

1.00

 Other

1.11

0.69–1.81

0.657

1.12

0.74–1.71

0.582

Education

 Incomplete secondary

0.68

0.40–1.15

0.151

0.72

0.47–1.11

0.139

 Secondary

0.77

0.50–1.21

0.259

0.79

0.55–1.15

0.220

 Vocational

0.77

0.58–1.02

0.074

0.78

0.61–1.02

0.068

 University

1.00

1.00

 Unknown

0.38

0.11–1.31

0.126

0.40

0.11–1.50

0.176

Marital status

 Married

1.00

1.00

 Cohabitation

0.77

0.53–1.12

0.169

0.75

0.54–1.06

0.107

 Single

0.78

0.55–1.12

0.181

0.75

0.55–1.03

0.078

Parity

<0.001^c

<0.001^c

 0

1.63

1.33–2.00

1.62

1.36–1.93

 1

1.44

1.08–1.92

1.40

1.08–1.83

  ≥ 2

1.00

1.00