Journal of Pregnancy / 2012 / Article / Tab 1

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 dayTotal
01–910+a

Number of participants12762632431,782
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 cigarettes05130
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 (%)50.651.551.950.90.800
 1 (%)32.333.729.232.1
 2+ (%)17.114.818.917.0
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 (%) 9.715.922.812.40.000
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 (%)14.625.037.319.2
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 (%)52.850.851.052.30.760
Paternal prenatal smoking (%)23.457.164.933.80.000
Parental postnatal smoking (%) 16.468.676.332.30.000
Child’s sex (male, %)53.448.147.751.80.125
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 (%) 12.715.821.114.30.004
Condition/medicine (%)2.73.45.33.20.104
Impaired hearing (%)4.64.27.04.80.229
Impaired vision (%) 2.42.37.83.10.000

Data are presented as medians (10/90 percentiles), unless otherwise specified.
aRange 10–25 cigarettes/day.
b values for unweighted data.