Table 2.

Risk of breast cancer in relation to pregnancy-related factors: Collaborative Breast Cancer Study (1996–2001)

	Cases (N=1,706)	Controls (N=1,756)	OR*	95% CI
Recency of last birth
Nulliparous	274	255	1.00	Ref
>10 years	952	1053	1.12	0.85–1.47
>5–10 years	275	272	1.22	0.85–1.73
≤5 years	205	176	1.35	0.90–2.02
p trend			0.14
Breast-feeding duration†
None	649	680	1.00	Ref
≤3 months	357	406	0.85	0.70–1.04
>3 months	426	415	1.10	0.91–1.34
p trend			0.39
Weight Change‡
<20%	416	418	1.00	Ref
20% – ≤29%	496	526	0.92	0.76–1.11
≥29%	417	463	0.87	0.72–1.07
p trend			0.18

^*Adjusted for age, state, parity, age at first birth, education, mammogram in last 5 years, family history, body-mass index, benign breast disease.

^†Duration of breast-feeding the last-born child; parous women only.

^‡Weight gain in final pregnancy relative to the most recent reported BMI; parous women only.