Table 4.

Multivariable odds ratios relating maternal smoking to low birth weight and pre-term birth with adjustment for age and one additional covariate among mothers in San Bernardino County, 2007–2008

	2007			2008
	Never smoker	Smoker during pregnancy	Smoking cessation during pregnancy	Never smoker	Smoker during pregnancy	Smoking cessation during pregnancy
	n = 31,050	n = 1,430	n = 626	n = 29,989	n = 1,355	n = 648
Low birth weight
Age	0.56 (0.47, 0.68)	1.00 (Reference)	0.57 (0.39, 0.85)	0.54 (0.44, 0.65)	1.00 (Reference)	0.72 (0.50, 1.02)
Age + ethnicity	0.57 (0.47, 0.69)	1.00 (Reference)	0.58 (0.39, 0.86)	0.53 (0.43, 0.64)	1.00 (Reference)	0.72 (0.51, 1.03)
Age + education	0.59 (0.49, 0.71)	1.00 (Reference)	0.59 (0.40, 0.88)	0.55 (0.45, 0.66)	1.00 (Reference)	0.73 (0.51, 1.04)
Age + WIC	0.55 (0.46, 0.67)	1.00 (Reference)	0.57 (0.38, 0.85)	0.55 (0.45, 0.66)	1.00 (Reference)	0.73 (0.51, 1.03)
Age + trimester     prenatal care began	0.60 (0.49, 0.72)	1.00 (Reference)	0.61 (0.41, 0.91)	0.56 (0.46, 0.68)	1.00 (Reference)	0.73 (0.51, 1.04)
Age + primary source of payment for prenatal care	0.60 (0.49, 0.72)	1.00 (Reference)	0.62 (0.42, 0.93)	0.55 (0.45, 0.67)	1.00 (Reference)	0.76 (0.53, 1.08)
Pre-term birth
Age	0.68 (0.58, 0.79)	1.00 (Reference)	0.69 (0.51, 0.92)	0.68 (0.58, 0.80)	1.00 (Reference)	0.69 (0.51, 0.93)
Age + ethnicity	0.62 (0.53, 0.73)	1.00 (Reference)	0.68 (0.50, 0.91)	0.66 (0.56, 0.77)	1.00 (Reference)	0.69 (0.51, 0.93)
Age + education	0.72 (0.61, 0.84)	1.00 (Reference)	0.73 (0.54, 0.98)	0.73 (0.54, 0.98)	1.00 (Reference)	0.73 (0.54, 0.98)
Age + WIC	0.67 (0.58, 0.78)	1.00 (Reference)	0.69 (0.51, 0.93)	0.69 (0.58, 0.80)	1.00 (Reference)	0.69 (0.51, 0.93)
Age + trimester prenatal care began	0.76 (0.65, 0.89)	1.00 (Reference)	0.75 (0.55, 1.02)	0.75 (0.63, 0.88)	1.00 (Reference)	0.74 (0.55, 1.01)
Age + primary source of payment for prenatal care	0.75 (0.64, 0.88)	1.00 (Reference)	0.77 (0.57, 1.04)	0.74 (0.63, 0.87)	1.00 (Reference)	0.76 (0.56, 1.02)