Effects of Tobacco Smoking in Pregnancy on Offspring Intelligence at the Age of 5

Table 3

Maternal smoking in pregnancy and the risk of low IQ.

Average number of cigarettes/day	Crude	Adjusted for core confounders^a	Adjusted for potential confounders^b
	OR (95% CI)	OR (95% CI)	OR (95% CI)
Full-scale IQ
0	1.00	1.00	1.00
1–9	1.60 (0.94, 2.70)	1.39 (0.78, 2.48)	1.52 (0.78, 2.99)
10+	1.31 (0.74, 2.31)	1.02 (0.56, 1.85)	1.06 (0.55, 2.19)
Verbal IQ
0	1.00	1.00	1.00
1–9	1.78 (1.03, 3.09)	1.49 (0.81, 2.73)	1.65 (0.85, 3.22)
10+	1.19 (0.64, 2.19)	0.90 (0.48, 1.69)	0.94 (0.50, 1.75)
Performance IQ
0	1.00	1.00	1.00
1–9	1.19 (0.69, 2.05)	1.08 (0.59, 1.95)	1.04 (0.54, 2.03)
10+	1.65 (0.97, 2.79)	1.41 (0.81, 2.48)	1.31 (0.65, 2.62)

^aParental education, maternal IQ, prenatal maternal alcohol consumption, the child’s sex, age at testing, and tester.
^bParental education, maternal IQ, prenatal maternal alcohol consumption, the child’s sex, age at testing, and tester, maternal age, parity, maternal marital status, prenatal paternal smoking, postnatal parental smoking, breast feeding, maternal prepregnancy BMI, the child’s sex, age at testing, health status, family/home environment.