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Table 3 Univariable analysis of risk factors for low birth weight, 1997/98 São Luís birth cohort

From: Low birth weight in São Luís, northeastern Brazil: trends and associated factors

Variables % Low birth weight Odds ratio* 95% Confidence interval p**
Newborn’s sex     0.701
 Male 7.4 1 Reference  
 Female 7.8 1.06 (0.78; 1.43)  
Preterm birth     <0.001
 Yes 31.6 10.42 (7.55; 14.38)  
 No 4.2 1 Reference  
IUGR***     <0.001
 No 3.1 1 Reference  
 Mild 5.1 1.66 (0.81; 3.41)  
 Moderate 11.9 4.23 (2.25; 7.97)  
 Severe 74.3 90.34 (57.02; 143.12)  
Maternal age (years)     0.005
 <18 12.9 2.00 (1.37; 2.93)  
 18 – 19 6.6 0.95 (0.61; 1.47)  
 20 – 34 6.9 1 Reference  
 ≥35 6.9 1.00 (0.45; 2.22)  
Maternal schooling (years)     0.197
 0 - 4 7.7 2.39 (0.82; 6.91)  
 5 - 8 8.3 2.61 (0.94; 7.26)  
 9 - 11 7.3 2.27 (0.81; 6.63)  
 ≥12 3.4 1 Reference  
Marital status     0.340
 Married 6.4 1 Reference  
 Consensual union 8.2 1.30 (0.89; 1.88)  
 Without a companion 8.0 1.27 (0.83; 1.94)  
Family income (minimum wages)     0.073
 ≤1 9.3 1.25 (0.87; 1.78)  
 1- 3 7.8 1.52 (1.00; 2.32)  
 >3 6.3 1 Reference  
 Missing 11.3 1.89 (1.09; 3.29)  
Maternal smoking during pregnancy     0.036
 No 7.4 1 Reference  
 Yes 13.5 1.95 (1.09; 3.50)  
Occupation of the family head     0.677
 Non-manual 6.8 1 Reference  
 Skilled manual worker 7.9 1.18 (0.78; 1.78)  
 Unskilled manual worker 7.4 1.10 (0.70; 1.70)  
 Missing 10.8 1.65 (0.70; 3.90)  
Parity     0.001
 1 9.6 1.72 (1.19; 2.48)  
 2 5.8 1 Reference  
 ≥3 5.5 0.94 (0.57; 1.53)  
Adequacy of prenatal care use     0.850
 Adequate 7.9 1 Reference  
 Inadequate 7.1 0.89 (0.64; 1.23)  
 No care 8.5 1.09 (0.63; 1.87)  
 Missing 8.6 1.09 (0.33; 3.64)  
Category of delivery care     0.133
 Private 4.5 1 Reference  
 Public 8.0 1.45 (0.87; 2.43)  
Type of delivery     0.027
 Vaginal 7.5 1 Reference  
 Cesarean 7.9 1.85 (1.02; 3.38)  
  1. *Odds Ratio (OR) calculated by simple logistic regression.
  2. **p-value calculated by the log likelihood ratio test.
  3. ***IUGR–intrauterine growth restriction based on the birth weight ratio.