The association between induced and spontaneous abortion and risk of breast cancer in Slovenian women aged 25-54

The risk of breast cancer may be increased by induced or spontaneous aborti on. The evidence for this association was evaluated in a population based c ase-control study in Slovenia, where 624 women aged 25-54 years with breast cancer diagnosed during 1988-1990 were matched for age and site of residen ce with controls randomly selected from the Slovenian Population Registry. Odds ratios (OR) and 95% confidence intervals (CI) were obtained by conditi onal logistic regression analyses. Spontaneous abortion was not associated with a significantly increased risk of breast cancer (nulliparous women: OR = 1.41, 95% CI 0.22-9.01; uniparous women: OR = 0.98, 95% CI 0.50-1.91; wo men with parity 2 or more: OR = 1.40, 95% CI 0.91-2.15). Induced abortion w as not associated with a statistically significant elevated risk. The risk of breast cancer was higher in nulliparous women (OR = 2.49, 95% Cl 0.68-9. 09), and was less among women who had more deliveries. In uniparous women, the risk of breast cancer appeared higher when the induced abortion took pl ace before a first full-term pregnancy (OR = 1.94, 95% CI 0.70-5.39) rather than after a first full-term pregnancy (OR = 1.22, 95% CI 0.71-2.10) but n either of these odds ratios reached significance. We found no significant a ssociation between spontaneous abortion or induced abortion and breast canc er risk. This study found an elevated, but not statistically significant, r isk associated with induced abortion among nulliparous women and among paro us women when the induced abortion was before the first full-term pregnancy . (C) 2000 Harcourt Publishers Ltd.