Table 2
Association (linear regression coefficients) between birth weight for gestational age and intelligence among one randomly selected sibling from the sibling pairs (n = 235)
| Mean difference in cognitive function score (95% CI) across thirds of the birth weight for gestational age and sex z score distribution | |||||
|---|---|---|---|---|---|
| Crude | Maternal age and race and birth order adjusted | Maternal age and race, birth order, and maternal smoking during pregnancy adjusted | Maternal age and race, birth order, maternal smoking during pregnancy, and family income adjusted | Maternal age and race, birth order, maternal smoking during pregnancy, family income, and parental education adjusted | |
| *p Value for linear trend across thirds of the distribution of birth weight for sex and gestational age z score. Variables in italics in the table columns are those variables that have been added to the subsequent model. | |||||
| Peabody picture vocabulary test (PPVT-R) at age 5 | |||||
| Lowest third of birth weight for gestational age distribution | 0 | 0 | 0 | 0 | 0 |
| Middle third of birth weight for gestational age distribution | 2.03 (−1.33 to 5.40) | 2.11 (−1.27 to 5.50) | 2.07 (−1.31 to 5.45) | 2.02 (−1.33 to 5.38) | 2.01 (−1.34 to 5.37) |
| Highest third of birth weight for gestational age distribution | 3.77 (0.35 to 7.99) | 4.43 (1.00 to 7.85) | 3.79 (0.37 to 7.22) | 3.78 (0.36 to 7.20) | 3.79 (0.03 to 7.55) |
| Mean difference per one unit increase in birth weight for gestational age and sex z score | 1.29 (0.00 to 2.59) | 1.48 (0.15 to 2.81) | 1.31 (0.02 to 2.60) | 1.29 (0.00 to 2.59) | 1.32 (0.03 to 2.62) |
| p linear trend* | 0.04 | <0.001 | 0.02 | 0.04 | 0.02 |
| Raven’s standard progressive matrix test at age 14 | |||||
| Lowest third of birth weight for gestational age distribution | 0 | 0 | 0 | 0 | 0 |
| Middle third of birth weight for gestational age distribution | 0.87 (−1.07 to 3.81) | 0.92 (−1.03 to 2.87) | 0.85 (−1.06 to 2.76) | 0.84 (−1.06 to 2.75) | 0.85 (−1.06 to 2.76) |
| Highest third of birth weight for gestational age distribution | 1.90 (−0.02 to 2.83) | 1.98 (0.05 to 3.91) | 1.91 (−0.01 to 3.85) | 1.87 (−0.05 to 3.79) | 1.88 (−0.03 to 3.79) |
| Mean difference per one unit increase in birth weight for gestational age and sex z score | 0.75 (0.01 to 1.51) | 0.82 (0.05 to 1.59) | 0.75 (0.01 to 1.48) | 0.73 (0.00 to 1.46) | 0.73 (0.00 to 1.47) |
| p linear trend* | 0.01 | <0.001 | 0.03 | 0.05 | 0.04 |
| Wide range achievement 3 reading test at age 14 | |||||
| Lowest third of birth weight for gestational age distribution | 0 | 0 | 0 | 0 | 0 |
| Middle third of birth weight for gestational age distribution | 0.84 (−1.04 to 2.72) | 0.85 (−1.04 to 2.73) | 0.73 (−1.15 to 2.61) | 0.73 (−1.15 to 2.61) | 0.75 (−1.17 to 2.58) |
| Highest third of birth weight for gestational age distribution | 1.83 (−0.05 to 3.71) | 1.86 (−0.02 to 3.74) | 1.52 (−0.32 to 3.40) | 1.50 (−0.33 to 3.38) | 1.28 (−0.55 to 3.15) |
| Mean difference per one unit increase in birth weight for gestational age and sex z score | 0.72 (0.00 to 1.44) | 0.75 (0.02 to 1.46) | 0.58 (−0.15 to 1.29) | 0.56 (−0.16 to 1.27) | 0.45 (−0.27 to 1.16) |
| p linear trend* | 0.04 | 0.007 | 0.43 | 0.45 | 0.56 |
