Table 1.
Descriptive data for the study sample (n = 94).
| Variable | n | Mean ± SD | Median | Range | Percent |
|---|---|---|---|---|---|
| Infant characteristics | |||||
| Sex (% males) | 94 | 63.8 | |||
| Age at 6.5-month testing (weeks) | 91 | 30.4 ± 3.5 | 29.9 | 25.6–40.9 | |
| Age at 11-month testing (weeks) | 90 | 50.5 ± 6.9 | 47.8 | 43.2–81.1 | |
| Birth weight (g) | 94 | 3566.7 ± 461.8 | 3,550 | 2,440–4,560 | |
| Gestation duration (weeks) | 94 | 39.2 ± 1.5 | 39.0 | 36.0–42.0 | |
| Adoption status (% adopted) | 94 | 10.6 | |||
| Maternal and family characteristics | |||||
| Age at prenatal interview (years) | 94 | 24.6 ± 5.8 | 24.3 | 15.3–39.0 | |
| Parity (no. of live births) | 94 | 2.1 ± 1.8 | 2 | 0–9 | |
| Marital status (% married or living with someone) | 94 | 69.1 | |||
| Breastfeeding (weeks) (% yes)a | 93 | 26.3 ± 17.1 | 24.3 | 0.1–57.3 | 87.1 |
| Social environment composite measureb | 94 | 0.0 ± 0.5 | 0.1 | –1.3–1.3 | |
| Maternal education (years) | 94 | 8.9 ± 1.7 | 9.0 | 5.5–14.3 | |
| Maternal nonverbal reasoning abilitiesc | 94 | 34.6 ± 8.1 | 36 | 13–48 | |
| Socioeconomic statusd | 94 | 25.5 ± 9.5 | 24.8 | 8–44 | |
| HOMEe | 85 | 31.6 ± 5.2 | 32 | 19–41 | |
| Language at interview (% Inuktitut) | 94 | 18.1 | |||
| Maternal consumption during pregnancy | |||||
| Cigarettes (no./day) (% yes)f | 94 | 10.8 ± 5.7 | 10.3 | 1–25 | 93.6 |
| Binge drinking (≥ 5 standard drinks of alcohol per occasion) (% yes) | 94 | 39.4 | |||
| Marijuana (% yes) | 94 | 40.4 | |||
| Contaminants and nutrients | |||||
| Cord plasma PCB-153 (μg/kg lipids) | 92 | 114.8 ± 96.0 | 78.1 | 12.0–550.9 | |
| Cord blood Hg (μg/L) | 91 | 22.5 ± 16.6 | 17.0 | 2.4–97.3 | |
| Cord blood Pb (μg/dL) | 93 | 4.8 ± 3.5 | 3.5 | 0.5–17.8 | |
| Cord plasma DHA (% phospholipids) | 90 | 3.7 ± 1.2 | 3.7 | 1.3–7.5 | |
| Cord blood Se (μg/L) | 91 | 296.4 ± 122.8 | 268.5 | 67.9–915.9 | |
| FTII | |||||
| Novelty preference, 6.5 months (%) | 89 | 57.9 ± 6.2 | 58.0 | 39.0–74.0 | |
| Novelty preference, 11 months (%) | 89 | 59.5 ± 6.3 | 59.4 | 38.0–74.0 | |
| Fixation duration, 6.5 months (sec) | 89 | 1.9 ± 0.4 | 1.8 | 1.0–3.2 | |
| Fixation duration, 11 months (sec) | 89 | 1.7 ± 0.3 | 1.6 | 1.2–2.6 | |
| A-not-B | |||||
| Length of delay–2 correct | 77 | 1.8 ± 2.2 | 0 | 0–9 | |
| Length of delay–3 correct | 77 | 1.4 ± 2.0 | 0 | 0–7 | |
| Perseverative errors (%) | 73 | 19.6 ± 15.6 | 17.7 | 0–69 | |
| BSID-II | |||||
| MDI | 87 | 94.2 ± 7.6 | 95 | 76–115 | |
| PDI | 87 | 89.5 ± 11.5 | 89 | 58–120 | |
| WISC-IV at 11 years | |||||
| Full-Scale IQ | 64 | 88.8 ± 8.7 | 88 | 72–108 | |
| Disruptive Behavior Scale at 11 years | |||||
| ADHD | 60 | 30.0 | |||
| aFor breastfed children, at 11-month visit. bComputed by calculating the average of the z-scores obtained for SES, maternal education, Raven, HOME, and language used at interview. cAssessed with the Hollingshead index (Hollingshead 2011). dBased on the Raven Progressive Matrices (Raven et al. 1992). eAssessed with the HOME inventory (Bradley and Caldwell 1979). fFor mothers who smoked. | |||||