Table 3.

Associations of Maternal Prenatal Smoking and Childhood Secondhand Smoke Exposure with Pubertal Onset^a, Crude and Adjusted Time Ratios (TRs) with 95% Confidence Intervals (CIs)

Smoke exposure	Crude model		Adjusted modelb		Adjusted model including both smoke exposuresc
	Breast Onset TR (95% CI)	Pubic Hair Onset TR (95% CI)	Breast Onset Adjusted TR (95% CI)	Pubic Hair Onset Adjusted TR (95% CI)	Breast Onset Adjusted TR (95% CI)	Pubic Hair Onset Adjusted TR (95% CI)
Maternal Prenatal Smoke
≥5 cigs/day	0.95 (0.90–1.00)	0.91 (0.86–0.97)	1.02 (0.96–1.06)	0.92 (0.87–0.97)	1.02 (0.96–1.06)	0.94 (0.89–1.01)
<5 cigs/day	0.98 (0.94–1.02)	0.97 (0.93–1.01)	1.01 (0.97–1.05)	0.98 (0.94–1.03)	1.01 (0.97–1.05)	1.00 (0.96–1.04)
None	ref	ref	ref	ref	ref	ref
Secondhand smoke d
High	0.96 (0.92–0.99)	0.91 (0.88–0.95)	1.00 (0.96–1.04)	0.94 (0.90–0.97)	0.99 (0.96–1.03)	0.95 (0.91–0.98)
Low/Moderate	0.98 (0.96–1.00)	0.98 (0.96–1.00)	1.01 (0.99–1.03)	1.00 (0.97–1.02)	1.01 (0.98–1.03)	1.00 (0.98–1.02)
None	ref	ref	ref	ref	ref	ref

^aPubertal onset defined (separately) as breast or pubic hair development at Tanner stage 2 or higher (B2+ or PH2+).

^bAdjusted model includes: child race, study site, household income, primary caregiver’s education, maternal age at delivery, child BMI (baseline), and birth weight, in separate models for each exposure.

^cAdjusted model includes both smoking variables, along with the above covariates.

^dSecondhand smoke categories determined from combination of number of cigarettes smoked in the home and hours exposed away from home. No exposure reflects no regular household smokers in the home or exposure outside (>1hr/week), High is defined as >35 cigarettes smoked per week in home or > 5 hours/week secondhand smoke exposure outside the home and at least one regular smoker at home, and Low/Moderate includes everyone else with at least some exposure at home or away.