Research Article
Effects of Tobacco Smoking in Pregnancy on Offspring Intelligence at the Age of 5
Table 1
Sample characteristics across levels of maternal cigarette smoking in pregnancy.
| | Average number of cigarettes per day | Total | | 0 | 1–9 | 10+a |
| Number of participants | 1276 | 263 | 243 | 1,782 | | Timing of interview (gestational week) | 17.0 (13.0/24.0) | 16.0 (12.0/24.0) | 17.0 (13.0/24.0) | 17.0 (13.0/24.0) | 0.608 | Median number of cigarettes | 0 | 5 | 13 | 0 | | Maternal age (years); mean (SD)
| 31.0 (4.2) | 30.2 (4.9) | 30.5 (4.8) | 30.8 (4.4) | 0.019 | Parity | | | | | | 0 (%) | 50.6 | 51.5 | 51.9 | 50.9 | 0.800 | 1 (%) | 32.3 | 33.7 | 29.2 | 32.1 | 2+ (%) | 17.1 | 14.8 | 18.9 | 17.0 | Maternal Body Mass Index (kg/m2) | 22.7 (19.6/29.0) | 22.5 (19.7/28.4) | 22.3 (19.2/28.4) | 22.6 (19.6/28.7) | 0.810
| Single mother (%)
| 9.7 | 15.9 | 22.8 | 12.4 | 0.000 | Parental education (years)
| 13.0 (11.0/16.5) | 12.5 (10.5/15.5) | 12.0 (10.5/14.5) | 13.0 (11.0/16.0) | 0.000 | Suboptimal home environment (%) | 14.6 | 25.0 | 37.3 | 19.2 | | Maternal IQ; mean (SD) | 101.6 (14.8) | 96.6 (14.8) | 95.2 (14.7) | 100.0 (15.0) | 0.000 | Maternal alcohol consumption in pregnancy (%) | 52.8 | 50.8 | 51.0 | 52.3 | 0.760 | Paternal prenatal smoking (%) | 23.4 | 57.1 | 64.9 | 33.8 | 0.000 | Parental postnatal smoking (%)
| 16.4 | 68.6 | 76.3 | 32.3 | 0.000 | Child’s sex (male, %) | 53.4 | 48.1 | 47.7 | 51.8 | 0.125 | Age at testing (years) | 5.2 (5.1/5.3) | 5.2 (5.1/5.3) | 5.2 (5.1/5.3) | 5.2 (5.1/5.3) | 0.551
| Birth weight (grams) | 3649.0 (513.1) | 3546.4 (492.9) | 3424.1 (508.8) | 3603.2 (515.5) | 0.000 | Gestational age (days) | 282.0 (268.0/293.0) | 282.0 (267.0/292.0) | 280.0 (267.0/294.0) | 281.0 (267.0/293.0) | 0.229
| Breast feeding ≤ 1 month (%)
| 12.7 | 15.8 | 21.1 | 14.3 | 0.004 | Condition/medicine (%) | 2.7 | 3.4 | 5.3 | 3.2 | 0.104 | Impaired hearing (%) | 4.6 | 4.2 | 7.0 | 4.8 | 0.229 | Impaired vision (%)
| 2.4 | 2.3 | 7.8 | 3.1 | 0.000 |
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Data are presented as medians (10/90 percentiles), unless otherwise specified.
aRange 10–25 cigarettes/day.
b values for unweighted data.
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