The Problem of Confounding in Studies of the Effect of Maternal Drug Use on Pregnancy Outcome

Table 10

Effect of stepwise adjustment for maternal characteristics in the analysis of the risk for drug-treated ADHD in infants conceived by IVF [34].

Variables adjusted for	OR	95% CI
None (=crude)	0.71	0.62–0.81
Year of delivery	0.77	0.68–0.87
Year of delivery, maternal age, parity, smoking and country of birth	0.91	0.81–1.05
Year of delivery, maternal age, parity, smoking, country of birth, and BMI	0.95	0.83–1.08
Year of delivery, maternal age, parity, smoking, country of birth, and education	1.14	0.99–1.31
Year of delivery, maternal age, parity, smoking, country of birth, and education, with exclusion of non-cohabiting women	1.18	1.05–1.36