Table 2.

Multivariate-adjusted proportional hazards ratios for the association of maternal and intrauterine estrogen-related exposures and relative timing of menarche

	n (%)	Adjusted for age and race/ethnicitya			Adjusted for age, race/ethnicity, and waist circumferencea
		Hazards ratio	95% confidence interval	p value	Hazards ratio	95% confidence interval	p value
Birth weightb(g)
Low (≤2,500)	19 (5%)	1.28	0.75, 2.18	0.37	1.17	0.69, 2.00	0.56
Normal (2,500–4,000)	315 (90%)	1.00	Reference		1.00	Reference
High (≥4,000)	14 (4%)	1.08	0.53, 2.20	0.84	1.01	0.49, 2.07	0.98
As a continuous variable		1.00	1.00, 1.00	0.33	1.00	1.00, 1.00	0.14
Gestational ageb(weeks)
<36	12 (3%)	1.65	0.85, 3.19	0.14	1.61	0.83, 3.10	0.16
36–41	281 (81%)	1.00	Reference		1.00	Reference
≥42	55 (16%)	1.03	0.72, 1.49	0.86	1.08	0.75, 1.55	0.69
As a continuous variable		1.00	0.99, 1.01	0.51	1.00	0.99, 1.01	0.66
Presence of severe pregnancy-induced nauseac
No	277 (91%)	1.00	Reference		1.00	Reference
Yes	26 (9%)	0.93	0.61, 1.43	0.75	0.87	0.57, 1.34	0.53
Mother’s age at menarched(years)
<12	106 (25%)	1.49	1.14, 1.93	0.003	1.45	1.12, 1.90	0.006
12–13	233 (56%)	1.00	Reference		1.00	Reference
>13	79 (19%)	0.55	0.40, 0.77	0.004	0.51	0.37, 0.71	<0.0001
As a continuous variable		0.79	0.73, 0.86	<0.0001	0.79	0.73, 0.86	<0.0001
Mother history of breast cancer	7 (2%)	2.60	1.14, 5.94	0.02	2.18	0.95, 4.98	0.06
2° family history of breast cancer	85 (19%)	1.12	0.85, 1.48	0.43	1.08	0.82, 1.42	0.59

^aBirth weight also adjusted for gestational age; gestational age also adjusted for birth weight

^b90 subjects missing birth weight and/or gestational age

^c90 subjects missing presence of severe pregnancy-induced nausea

^d20 subjects missing mother’s age at menarche