APPENDIX TABLE 2.
Conditional models of the association between maternal smoking during pregnancy and children's mental and physical development among all siblings (n = 16,619) in the Collaborative Perinatal Project, 1959–1974*
| Mean or % (standard error) | Level of maternal smoking during pregnancy (cigarettes/day) |
F (3 df) | p value | ||||||
| 1–9 |
10–19 |
≥20 |
|||||||
| OR† or β‡ | 95% CI† | OR or β | 95% CI | OR or β | 95% CI | ||||
| Birth | |||||||||
| Birth weight (g) | 3,203.0 (4.2) | −10.6 | −44.8, 23.5 | −78.0 | −119.6, −36.4 | −98.8 | −143.1, −54.6 | 8.4 | <0.001 |
| 5-minute Apgar score | 9.0 (0.0) | −0.01 | −0.11, 0.08 | 0.05 | −0.07, 0.17 | 0.02 | −0.11, 0.15 | 0.4 | 0.727 |
| Age 4 years | |||||||||
| Stanford-Binet IQ† | 97.3 (0.1) | 0.12 | −1.04, 1.30 | 0.31 | −1.18, 1.80 | 0.51 | −1.04, 2.06 | 0.1 | 0.938 |
| Age 7 years | |||||||||
| Neurologic soft signs (%) | 12.2 (0.0) | 0.93 | 0.66, 1.30 | 0.90 | 0.60, 1.34 | 1.02 | 0.66, 1.59 | 0.2 | 0.886 |
| Wechsler verbal IQ | 93.3 (0.1) | −0.42 | −1.42, 0.59 | −0.58 | −1.89, 0.72 | 0.33 | −0.98, 1.64 | 1.1 | 0.371 |
| Wechsler performance IQ | 98.1 (0.1) | −0.29 | −1.52, 0.94 | −0.63 | −2.25, 0.99 | 0.34 | −1.28, 1.96 | 0.7 | 0.546 |
| Wechsler full-scale IQ | 95.1 (0.1) | −0.40 | −1.45, 0.65 | −0.64 | −1.98, 0.70 | 0.37 | −0.99, 1.72 | 1.1 | 0.343 |
| WRAT† spelling score | 95.4 (0.1) | −0.32 | −1.27, 0.64 | −0.56 | −1.76, 0.65 | −0.56 | −1.83, 0.71 | 0.3 | 0.808 |
| WRAT reading score | 97.8 (0.1) | −0.38 | −1.53, 0.77 | −1.54 | −1.58, 1.27 | −0.36 | −1.88, 1.17 | 0.2 | 0.909 |
| WRAT arithmetic score | 96.1 (0.1) | −0.60 | −1.58, 0.29 | −0.98 | −2.06, 0.11 | −0.12 | −1.29, 1.06 | 1.6 | 0.188 |
| Body mass index§ | 15.9 (0.0) | 0.06 | −0.12, 0.25 | 0.18 | −0.05, 0.41 | 0.18 | −0.07, 0.43 | 1.0 | 0.383 |
| Overweight¶ (%) | 3.9 (0.0) | 1.34 | 0.72, 2.39 | 1.82 | 0.85, 3.87 | 1.74 | 0.83, 3.70 | 1.0 | 0.378 |
| Conduct problems scale score | 0.2 (0.0) | 0.03 | −0.05, 0.11 | 0.04 | −0.05, 0.13 | 0.04 | −0.06, 0.14 | 0.3 | 0.814 |
| Asthma (%) | 4.7 (0.0) | 0.89 | 0.53, 1.49 | 0.88 | 0.54, 2.03 | 1.04 | 0.54, 2.03 | 0.2 | 0.896 |
Multiple imputation was used to generate 10 data sets with complete data for all Collaborative Perinatal Project siblings (n = 16,619) using the MI and MIANALYZE procedures in SAS, version 9.1.3 (33). Variables in the imputation model included all child outcomes, statistically significant correlates of smoking during pregnancy identified in the proportional odds model (shown in table 2), birth order, and sex. Linear regression coefficients (β) and odds ratios shown in the table were generated by combining results from the 10 multiply imputed data sets.
OR, odds ratio; CI, confidence interval; IQ, intelligence quotient; WRAT, Wide Range Achievement Test.
Odds ratios from logistic regression models are shown for neurologic soft signs, overweight, and asthma; linear regression coefficients (β) are shown for all other dependent variables.
Weight (kg)/height (m)2.
≥95th percentile of body mass index for age and sex.