Table 2.
Description of potential biological and health predictors of low IQ and unadjusted associations*
| 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) |
*Logistic regression analysis in children age 6. The 2004 Pelotas Birth Cohort Study.
CI = confidence intervals; OR = odds ratios; IQ = intelligence quotient.