Parity in relation to risk of axillary lymph node involvement in women with breast cancer.  Results from Swedish population-based series of 3,472 consecutive cases. 
To investigate the association between parity and axillary lymph node involvement (ALNI) at breast cancer diagnosis.  One surgeon has reviewed all breast cancer cases in Malmo, Sweden, diagnosed 1961-1991.  This study includes the 3,472 women who had a first-time diagnosis of unilateral invasive breast cancer, and who had undergone axillary dissection.  Information was collected regarding date of birth, date of diagnosis, age at diagnosis, menopausal status, tumour size, histological type, tumour location, type of surgery, stage (ALNI), and parity.  Parity was investigated in relation to ALNI using logistic regression analysis, adjusted for potential confounders, yielding odds ratios (OR) with 95% confidence intervals (CI).  The analyses were repeated in different strata with regard to birth-years cohort, age at diagnosis, and period of diagnosis.  High parity was associated with ALNI, the adjusted OR for ALNI among women with 4 or more children was 1.56 (1.13-2.15).  This association was stronger in comparatively old women (> or = 67.45 years), OR 1.78 (1.10-2.88).  Considering parity a continuous variable, the OR for ALNI among all women was 1.06 (1.01-1.12).  We conclude that women with 4 or more children had an increased risk of ALNI at breast cancer diagnosis.