. Author manuscript; available in PMC: 2011 May 6.

Published in final edited form as: Occup Environ Med. 2009 Oct;66(10):685–690. doi: 10.1136/oem.2008.043935

Table 2.

Associations of Birth Outcomes With Non-Occupational Risk Factors

Risk factor	Pre-term delivery		Small for gestational age		Small head circumference		Small abdominal circumference
Risk factor	OR^a (95% CI)	P	OR^a (95% CI)	P	OR^a (95% CI)	P	OR^a (95% CI)	P
Maternal age^b	1.01 (0.93-1.10)	0.8	1.04 (0.98-1.11)	0.2	0.99 (0.95-1.04)	0.8	1.05 (1.00-1.10)	0.07
Female baby	1.04 (0.58-1.89)	0.9	-		-		1.22 (0.85-1.76)	0.3
Consumed ≥14 units of alcohol per week before pregnancy	0.73 (0.33-1.63)	0.4	1.23 (0.74-2.04)	0.4	0.81 (0.50-1.31)	0.4	1.00 (0.64-1.57)	1.0
Smoked before pregnancy	0.63 (0.29-1.36)	0.2	1.59 (0.98-2.58)	0.06	1.08 (0.71-1.65)	0.7	1.43 (0.94-2.17)	0.09
Educational level^d	0.89 (0.70-1.12)	0.3	0.90 (0.75-1.07)	0.2	0.87 (0.75-1.01)	0.07	0.93 (0.81-1.08)	0.3
Primiparous	2.03 (1.04-3.95)	0.04	2.62 (1.55-4.42)	<0.001	1.51 (1.01-2.25)	0.04	2.22 (1.46-3.37)	<0.001
Maternal BMI before pregnancy^e	0.96 (0.89-1.03)	0.2	0.94 (0.89-1.00)	0.04	0.98 (0.94-1.02)	0.3	0.99 (0.95-1.03)	0.7

For each outcome, all risk factors were examined in a single logistic regression model, and odds ratios are therefore mutually adjusted.

Maternal age was analysed as a continuous variable. Risk estimates are for a one year increase in age.

Not applicable because outcome was adjusted for the sex of the baby.

Educational level was analysed as an ordinal variable with six levels defined as in Table 1. Risk estimates are for an increase of one level.

Maternal BMI was analysed as a continuous variable. Risk estimates are for an increase of 1 kg/m².