Table 2.

Associations of stimulant drug use in pregnancy with preterm birth and gestational age (in weeks), comparing the unadjusted, semi-adjusted, fully adjusted, and combined risk with smoking models, Boston Birth Cohort, 1998-2018 (N = 8261)^a

Model Type and Category	Preterm Birth		Gestational Age, in Weeks
	OR (95% CI)	P Valueb	β Coefficient (95% CI)	P Valueb
Unadjusted model: using stimulant drugs during pregnancy	1.70 (1.18-2.41)	.003	−0.78 (−1.33 to −0.22)	.01
Adjustedc model: using stimulant drugs during pregnancy	1.40 (0.95-2.04)	.08	−0.63 (−1.21 to −0.05)	.03
Fully adjusted modeld	1.00 [Reference]		1.00 [Reference]
Using stimulant drugs during pregnancy	1.19 (0.80-1.75)	.38	−0.35 (−0.95 to 0.25)	.25
Smoking during pregnancy	1.35 (1.14-1.60)	<.001	−0.52 (−0.77 to −0.27)	<.001
Combined risk modele
Not using stimulant drugs, not smoking during pregnancy	1.00 [Reference]		1.00 [Reference]
Using stimulant drugs, not smoking during pregnancy	0.69 (0.19-1.98)	.52	0.73 (−0.78 to 2.24)	.34
Not using stimulant drugs, smoking during pregnancy	1.33 (1.12-1.58)	.001	−0.49 (−0.78 to −0.24)	<.001
Using stimulant drugs and smoking during pregnancy	1.73 (1.14-2.59)	.01	−1.04 (−1.67 to −0.41)	.001

Abbreviation: OR, odds ratio.

^aData source: Wang et al.³⁵

^bUsing the Wald χ² test for all coefficients, with P < .05 considered significant.

^cIndependent effect of stimulant drug and alcohol use during pregnancy, adjusted for maternal age, sex of child, marital status, parity, body mass index of mother, annual household income, race/ethnicity, and education.

^dEffect of stimulant drug use during pregnancy independent of smoking, adjusted for alcohol use during pregnancy, maternal age, sex of child, marital status, parity, pre-pregnancy body mass index of mother, annual household income, race/ethnicity, and education.

^eCombined effects of using stimulant drugs and smoking during pregnancy compared with not using stimulant drugs and not smoking during pregnancy, adjusted for previously listed covariates.