Table 4.

Relative Risk of Renal Cell Cancer Associated with Parity, by Age at First Birth and Postmenopausal Hormone Use, Nurses’ Health Study, 1976–2004

	1–3 Childbirths			≥4 Childbirths
	No. of Cases	Multivariate RRa	95% CI	No. of Cases	Multivariate RRa	95% CI
Age at first birthb, years
≥26	25	1.00	Referent	24	1.47	0.89, 2.43
<26	83	1.46	1.00, 2.12	85	2.17	1.49, 3.14
Pinteraction	0.96
Postmenopausal hormone usec
Never use	31	1.00	Referent	24	1.14	0.67, 1.96
Ever use	61	0.89	0.57, 1.38	54	1.48	0.95, 2.32
Pinteraction	0.25

Abbreviations: CI, confidence interval; RR, relative risk.

^aAdjusted for history of hypertension (yes, no), body mass index (weight (kg)/height (m)²; <25, 25–26.9, 27–29.9, or ≥30), smoking status (never smoker or 1–19, 20–39, or ≥40 pack-years), fruit intake (servings/day; continuous), vegetable intake (servings/day; continuous), and alcohol intake (g/day; continuous).

^bAmong parous women only.

^cAmong postmenopausal women only.