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Table 2 Description of potential biological and health predictors of low IQ and unadjusted associations*

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

Characteristic Rate n (%) Low IQ n (%) Unadjusted OR (95% CI)
All 3523 (100) 594 (16.9)  
Intended pregnancy (n = 3521)    p = 0.0000
Intended 1554 (44.1) 206 (13.3) 1
Unintended 1967 (55.9) 386 (19.6) 1.6 (1.3–1.9)
Prenatal care visits (n = 3337)    p = 0.0000
<6 541 (16.2) 158 (29.2) 2.5 (2.1–3.2)
≥6 2796 (83.8) 390 (14.0) 1
Maternal hospitalization during pregnancy (n = 3522)    p = 0.5425
No 3147 (89.3) 534 (17.0) 1
Yes 375 (10.7) 59 (15.7) 0.9 (0.7–1.2)
Maternal mental disorder during the child’s first year of life (n = 3375)    p = 0.0000
No 2189 (64.9) 296 (13.5) 1
Yes 1186 (35.1) 268 (22.6) 1.9 (1.6–2.2)
Type of delivery (n = 3522)    p = 0.0000
Vaginal 1920 (54.5) 392 (20.4) 1.8 (1.5–2.2)
Cesarean section 1602 (45.5) 201 (12.6) 1
Gestational age (n = 3521)    p = 0.0009
<37 weeks 470 (13.4) 105 (22.3) 1.5 (1.2–1.9)
≥37 weeks 3051 (86.6) 488 (16.0) 1
Birth weight (n = 3522)    p = 0.0003
<2500 g 304 (8.6) 75 (24.7) 1.7 (1.3–2.3)
≥2500 g 3218 (91.4) 518 (16.1) 1
Health condition at birth (n = 3514)    p = 0.0078
No 3111 (88.5) 503 (16.2) 1
Yes 403 (11.5) 87 (21.6) 1.4 (1.1–1.8)
Child’s gender (n = 3522)    p = 0.0003
Female 1701 (48.3) 246 (14.5) 1
Male 1821 (51.7) 347 (19.1) 1.4 (1.2–1.7)
Child hospitalization during the first year of life (n = 3424)    p = 0.0000
No 2801 (81.8) 434 (15.5) 1
Yes 623 (18.2) 140 (22.5) 1.6 (1.3–2.0)
Duration of breastfeeding (n = 3512)    p = 0.0000
<1 month 364 (10.4) 98 (26.9) 2.2 (1.7–2.9)
1–11 months 1792 (51.0) 298 (16.6) 1.2 (1.0–1.5)
≥12 months 1356 (38.6) 194 (14.3) 1
Duration of exclusive breastfeeding (n = 3474)    p = 0.0000
<1 month 1265 (36.4) 258 (20.4) 2.8 (1.8–4.3)
1–5 months 1899 (54.7) 301 (15.9) 2.1 (1.4–3.1)
≥6 310 (8.9) 26 (8.4) 1
Weight-for-age deficit during the first year of life (n = 3522)    p = 0.0000
No 3099 (88.0) 476 (15.4) 1
Yes 423 (12.0) 117 (27.7) 2.1 (1.7–2.7)
Height-for-age deficit during the first year of life (n = 3523)    p = 0.0000
No 2918 (82.8) 436 (14.9) 1
Yes 604 (17.2) 157 (26.0) 2.0 (1.6–2.5)
Head circumference-for-age deficit during the first year of life (n = 3522)    p = 0.0000
No 3211 (91.2) 497 (15.5) 1
Yes 311 (8.8) 96 (30.9) 2.4 (1.9–3.2)
Weight-for-height deficit during the first year of life (n = 3521)    p = 0.0634
No 3334 (94.7) 551 (16.5) 1
Yes 187 (5.3) 41 (21.9) 1.4 (1.0–2.0)
Mother’s self-rated health (n = 3421)    p = 0.0000
Excellent/very good 1269 (37.1) 137 (10.8) 1
Good/fair/poor 2152 (62.9) 437 (20.3) 2.1 (1.7–2.6)
Maternal perception of the child’s health status (n = 3424)    p = 0.0000
Excellent/very good 2119 (61.9) 253 (11.9) 1
Good/fair/poor 1305 (38.1) 321 (24.6) 2.4 (2.0–2.9)
  1. *Logistic regression analysis in children age 6. The 2004 Pelotas Birth Cohort Study.
  2. CI = confidence intervals; OR = odds ratios; IQ = intelligence quotient.