TABLE 2.

Correlates of maternal smoking during pregnancy in the Collaborative Perinatal Project, 1959–1974^*

	Odds ratio	95% confidence interval
Socioeconomic status index	1.002	1.001, 1.003
Maternal age	0.978	0.973, 0.984
Paternal age	1.009	1.005, 1.014
Maternal marital status
Married	0.82	0.72, 0.92
Not married	1
Maternal employment status
Employed	0.88	0.84, 0.92
Not employed	1
Presence of father in the household
No	0.99	0.87, 1.12
Yes	1
Household crowding
Severely crowded (≥1.5 persons per room)	0.69	0.66, 0.72
Crowded (≥1 person per room)	0.90	0.86, 0.95
Not crowded (<1 person per room)	1
Paternal history of psychiatric or substance-use disorder
Hospitalized	1.39	1.15, 1.69
Outpatient	1.21	0.93, 1.59
Addiction	3.37	1.94, 5.88
Questionable	1.34	1.09, 1.65
None	1
Maternal history of psychiatric or substance-use disorder
Hospitalized	1.84	1.52, 2.23
Outpatient	1.68	1.43, 1.97
Questionable	1.94	1.60, 2.35
None	1
No. of prior pregnancies	1.07	1.06, 1.08
No. of psychiatric or neurologic problems during pregnancy	1.21	1.15, 1.27

^*Results from an ordinal logistic regression model of maternal smoking during pregnancy (n = 44,745). Odds ratios indicate the magnitude of risk for being in a higher category of maternal smoking (0, 1–9, 10–19, or ≥20 cigarettes/day). The model included Collaborative Perinatal Project mothers of liveborn singleton offspring with complete data on the covariates shown. Variance estimates were adjusted for the presence of multiple siblings per family using generalized estimating equations.