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Table 5 Linear regression analyses: Relationship between maternal exposure to smoking, preeclampsia and fetal growth

From: Smoking in preeclamptic women is associated with higher birthweight for gestational age and lower soluble fms-like tyrosine kinase-1 levels: a nested case control study

Model

Unadjusted β

(95% CI)

p-value

Adjusted β#

(95% CI)

p-value

Model 1a

z-score BWGA = smoker + preeclampsia + interaction term

    

Smoker

-0.29

(-0.51,-0.08)

0.008

-0.38

(-0.61, -0.15)

0.0013

Preeclampsia

-0.67

(-0.91,-0.43)

< 0.0001

-0.67

(-0.93, -0.41)

< 0.0001

Smoker* preeclampsia

0.86

(0.36, 1.36)

0.0008

0.86

(0.33, 1.39)

0.0015

Model 1b

z-score BWGA = smoker + preeclampsia + interaction term + z-score PWGA

    

Smoker

-0.30

(-0.50, -0.09)

0.004

-0.32

(-0.54, -0.09)

0.0067

Preeclampsia

-0.61

(-0.86, -0.35)

< 0.0001

-0.60

(-0.87, -0.33)

< 0.0001

Smoker* preeclampsia

0.74

(0.25, 1.23)

0.003

0.69

(0.16, 1.22)

0.0112

z-score PWGA

0.56

(0.48, 0.65)

< 0.0001

0.52

(0.43, 0.61)

< 0.0001

Model 2a

z-score BWGA = log hair nicotine + preeclampsia + interaction term

    

Log nicotine

-0.12

(-0.16, -0.05)

0.0004

-0.086

(-0.16, -0.01)

0.0234

Preeclampsia

-0.31

(-0.55, -0.07)

0.011

-0.36

(-0.63, -0.09)

0.0087

Log hair nicotine * preeclampsia

0.28

(0.11, 0.46)

0.002

0.26

(0.07, 0.46)

0.0091

Model 2b

z-score BWGA = log hair nicotine + preeclampsia + interaction term + z-score PWGA

    

Log nicotine

-0.09

(-0.16, -0.03)

0.005

-0.06

(-0.13, 0.01)

0.0912

Preeclampsia

-0.31

(-0.54, -0.08)

0.009

-0.33

(-0.60, -0.07)

0.0131

Log hair nicotine * preeclampsia

0.25

(0.07, 0.42)

0.007

0.25

(0.06, 0.44)

0.0095

z-score PWGA

0.56

(0.48, 0.64)

< 0.0001

0.52

(0.42, 0.62)

< 0.0001

  1. Dependent variable for all models: z-score birthweight for gestational age (BWGA), as defined in Kramer et al [14]
  2. PWGA = placental weight for gestational age; z-score PWGA calculated as defined by McNamara [15, 16]
  3. # analyses adjusted for age, pre-pregnancy body mass index, maternal language other than French or English, diabetes, chronic hypertension and parity (nullipara vs. other). For adjusted models 1a and 1b, diabetes was statistically significant (p = 0.03 and p = 0.03, respectively). No other variables were statistically significant in any of the models.
  4. R-square for models: Model 1a unadjusted, 0.057, Model 1a adjusted, 0.096; Model 1b unadjusted, 0.388, Model 1b adjusted, 0.391; Model 2a unadjusted, 0.062, Model 2a adjusted, 0.100; Model 2b unadjusted, 0.395, Model 2b adjusted, 0.384.