PARITY AND OTHER REPRODUCTIVE FACTORS AND RISK OF ADENOMATOUS POLYPS OF THE DISTAL COLORECTUM (UNITED-STATES)

Evidence for an effect of reproductive factors on colorectal carcinoge nesis is inconsistent and little is known about their role in developm ent of precursor adenomatous polyps, We evaluated the relation between reproductive factors and distal colorectal adenomas (n = 982) during 14 years of follow up of 26,983 participants in the Nurses' Health Stu dy (United States), The women were free of diagnosed cancer or polyps in 1980, underwent endoscopy 1980-94, and had reported on their parity , oral contraceptive (OC) use, and ages at menarche, first term-pregna ncy, and menopause, We calculated relative risks (RR) and 95 percent c onfidence intervals (CI) using multiple Logistic regression. Women wit h higher parity had an increased risk of adenomas of the distal colore ctum (P trend = 0.004; 6+ cfO parity: RR = 1.3, CI = 0.9-1.8) or dista l colon (P trend = 0.002, RR = 1.7, CI = 1.2-2.6). This association wa s significantly stronger among women with a family history of colorect al cancer (P interaction = 0.03); comparing 6+ term-pregnancies with n ulliparity, among those with a family history, the RR for distal colon adenoma Nas 3.2 (CI = 1.4-7.2), while among those without a family hi story, the RR was 1.3 (CT = 0.8-2.2), We observed no association for d istal colorectal adenoma and age at menarche, age at first term-pregna ncy, ever use of OCs, or menopausal status, Further work is needed to clarify the relation of parity with colon adenoma risk.