Opium use during pregnancy and infant size at birth: a cohort study

Table 4 Risk ratios (RR) and 95% confidence intervals (CI) for the associations between opium and tobacco use during pregnancy and risk of small head circumference at term birth

	Pregnancies	Small head circumference ^a	Crude	Adjusted ^b
	N	N (%)	RR (95% CI)	RR (95% CI)
Opium
Unexposed	850	45 (5.3)	Reference
Exposed	798	99 (12.4)	2.33 (1.64–3.32)	2.24 (1.55–3.24)
Tobacco and opium
Unexposed	850	45 (5.3)	Reference
Exposed to opium only	616	76 (12.3)	2.33 (1.61–3.36)	2.24 (1.53–3.29)
Exposed to tobacco and opium	182	23 (12.6)	2.36 (1.43–3.90)	2.23 (1.31–3.79)

^aSmall head circumference less than 33 cm (below the 5th percentile of head circumference of unexposed and term live birth)
^bAdjusted for: maternal age, height, BMI, parity, husband’s occupation, infant sex, weeks gestational age, and residential place

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