Since the incidence of breast cancer is increasing in young women and young women are more commonly delaying child-bearing, the issue of considering a pregnancy subsequent to the diagnosis and treatment of breast cancer is becoming more common. The impact of a subsequent pregnancy on disease progression and quality of life is, however, not well defined. We evaluated treatment outcome and quality of life among 23 breast cancer patients treated with conservative surgery and radiation among the 1624 patients treated at the Joint Center for Radiation Therapy between 1968 and 1985 who had subsequent pregnancies as compared with 23 patients without subsequent pregnancy matched by age and stage at diagnosis and time to pregnancy without recurrence. Quality of life was evaluated using two self-report measures, Ferrans and Powers Quality of Life Index and the Adaptation to Surviving Cancer Profile, and a measure of parenting stress (Parenting Stress Index). Results showed no differences in recurrence or distant metastasis between the matched groups. In addition, subjects with subsequent pregnancy perceived that family issues had the greatest impact on quality of life and were not at higher risk for parental stress due to breast cancer than the normal population. Both groups of young women perceived that they were able to adjust well after treatment. Study results are consistent with other clinical studies comparing patients with and without subsequent pregnancy who have failed to demonstrate a survival disadvantage.(ABSTRACT TRUNCATED AT 250 WORDS)