Table 4.

The association of HCB with studied outcomes according to maternal smoking status at the beginning of pregnancy. The association is shown for an eight units increase in HCB levels in human milk (μg/kg milk fat).

	Current or previous smoker		Nonsmoker
	β	95 % CI	β	95 % CI	p-value interaction
Birth weighta	−282	(−467 to −98)	0.50	(−149 to 150)	0.01
Head Circumferencea	−0.58	(−1.11 to −0.05)	0.37	(−0.06 to 0.80)	0.00
Crown-heel lengtha	−0.81	(−1.58 to −0.05)	0.33	(−0.29 to 0.94)	0.01
Ponderal Indexa	−0.11	(−0.22 to −0.01)	−0.05	(−.0.13 to 0.03)	0.30
Gestational ageb	−1.60	(−6.5 to 3.3)	−2.76	(−6.7 to 1.2)	0.70
	OR	95 % CI	OR	95 % CI	p-value interaction
SGAb	2.7	(0.99 to 7.6)	1.5	(0.6 to 3.3)	0.28
Growth restrictionb	3.3	(0.85 to 12.5)	1.4	(0.4 to 5.0)	0.32

Each estimate derives from a separate adjusted model.

^aAdjusted for gestational age (plus gestational age squared), infant’s sex, parity, maternal age, height, pre-pregnancy BMI, education, county of residence and the sum of 6 PCB congeners (CB-28, −52, −101, −138, −153, −180). Missing values have been imputed for 11 subjects. The analysis were based on 299 subjects for birth weight, 294 for ponderal index, and 295 for head circumference and crown-heel length, due to missing values on smoking or the respective outcomes.

^bAdjusted for the same variables except gestational age (and gestational age square) and infant’s sex.. One subject was excluded due to missing values for smoking status thus the analysis with SGA and growth restriction were based on 325 subjects, while gestational age was based on 299 subjects. Missing values have been imputed for 13 subjects.