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Table 2 Univariate analysis of possible confounding variables influencing birth weight, in premature infants (n = 189)

From: Smoking during pregnancy and harm reduction in birth weight: a cross-sectional study

Variable β SE p CI (β;95%)
Age at delivery (years) 5.5 18.0 0.762 (−30.4 to 41.3)
≤ 8 years of education − 282.55 262.65 0.282 (− 797.3 to 232.24)
9 to 11 years of education − 100.97 251.11 0.688 (− 593.14 to 391.19)
Employed 124.2 203.2 0.543 (−281.7 to 530.2)
Live with a partner 210.8 337.2 0.534 (− 462.7 to 884.4)
First pregnancy 8.0 24.7 0.745 (−41.2 to 57.3)
Interval between deliveries (years) 79.3 192.8 0.682 (− 305.8 to 464.3)
Pregestational obesity or overweight −136.5 114.3 0.234 (−361.9 to 89.0)
Prenatal care in public service 39.0 147.9 0.793 (− 253.8 to 331.7)
≥ 7 prenatal medical visitsb 401.7 111.7 0.000 (180.5 to 622.9)
 Alcohol consumption − 210.7 279.1 0.452 (− 763.2 to 341.7)
 Illegal drug use 97.9 682.7 0.886 (− 1253.5 to 1449.2)
Participation in prenatal groupb 203.1 118.6 0.089 (−31.7 to 437.9)
 Advised regarding warning signs −5.3 114.0 0.963 (− 230.9 to 220.3)
 Use of folic acid and iron sulfate −49.7 128.6 0.700 (− 304.3 to 204.9)
Emotional problemsb 321.0 223.3 0.154 (− 122.5 to 764.5)
 Anemia − 465.7 449.7 0.303 (− 1358.9 to 427.5)
High blood pressure/pre-eclampsia/ eclampsia/ HELLP syndromea, b − 469.5 303.7 0.126 (− 1072.7 to 133.6)
 Diabetes 314.7 328.7 0.341 (− 338.2 to 967.6)
Hyperemesisb − 690.8 437.4 0.118 (− 1559.5 to 177.9)
Hemorrhage/ bleeding/threatened abortionb − 442.1 321.8 0.173 (− 1081.3 to 197.1)
Infectionb − 522.3 300.1 0.085 (− 1118.3 to 73.8)
  1. aHELLP hemolysis, elevated liver enzymes, low platelet count
  2. bSelected as potential confounder