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Table 3 Final adjusted logistic regression model including early life predictors of low IQ at age 6

From: Early life determinants of low IQ at age 6 in children from the 2004 Pelotas Birth Cohort: a predictive approach

Predictor OR a(95% CI) p-value Weights
Male 1.5 (1.2–1.8) p = 0.0002 15
Skin color: both mother and father non-white 1.9 (1.5–2.1) p = 0.0000 25
Father unemployed at the child’s birth 1.6 (1.2–2.0) p = 0.0002 18
Mother unemployed during the child’s first 12 months of life 1.5 (1.2–1.8) p = 0.0003 15
Household income at the child’s birthb 1.3 (1.2–1.5) p = 0.0000 12b
Maternal educationb 1.8 (1.6–2.2) p = 0.0000 23b
Number of siblings at the child’s birth: 3 or more 1.8 (1.3–2.3) p = 0.0001 22
Number of persons per room at age 12 month: 3 or more 1.6 (1.3–2.0) p = 0.0000 18
At least one smoking parent during pregnancy 1.3 (1.1–1.6) p = 0.0145 10
Duration of breastfeeding   p = 0.0000  
<1 month 2.2 (1.6–3.1)   31
1–11 months 1.3 (1.0–1.6)   10
≥12 months 1   
Head circumference-for-age deficit during the first year of life 1.7 (1.2–2.4) p = 0.0022 20
Height-for-age deficit during the first year of life 1.3 (1.0–1.7) p = 0.0524 10
Maternal perception of the child’s health status (good/fair/poor)c 1.4 (1.2–1.8) p = 0.0009 14
  1. aAdjusted for child’s age, interview setting, IQ test evaluator.
  2. bThe effect indicates increased odds of low IQ by predictor category.
  3. cThe reference category is excellent/very good health.
  4. CI = confidence intervals; IQ = intelligence quotient.
  5. The 2004 Pelotas Birth Cohort (n = 3312).