Pregnancy after treatment of breast cancer in young women does not adversely affect the prognosis.

We assessed whether pregnancy after breast cancer in patients younger than 36 years of age affects the prognosis. Of 115 women with breast cancer followed for a mean of 6 years, 18 became pregnant (median time between diagnosis and the first pregnancy 44.5 months). Voluntary interruption of pregnancy was decided by 8 (44.4%) women. Significant differences in prognostic factors between pregnant and non-pregnant women were not observed. Pregnant women showed a lower frequency of positive estrogen receptors (41%) than non-pregnant (64%) (P=0.06). At 5 years of follow-up, 100% of women in the pregnant group and 80% in the non-pregnant group were alive. The percentages of disease-free women were 94% and 64%, respectively (P=0.009). Breast cancer patients presented a high number of unwanted pregnancies. Pregnancy after breast cancer not only did not adversely affect prognosis of the neoplasm but also may have a protective effect.