Abstract Background: The favorable outcome of mothers giving birth after breast cancer compared to those who do not, has been attributed to a healthy mother effect. Mainly former breast cancer patients with excellent health status and outlook proceed to having children after their disease. This study evaluates the excess mortality risk among these 'healthy mothers' and factors modifying this risk.Methods: By linking the Singapore Birth Registry (319'437 individuals) and Swedish Multi-Generation Cohort (11 million women) with the respective national cancer registries we identified all 509 women who gave birth >12 months after a breast cancer diagnosis. We calculated excess absolute mortality risks and Standardized Mortality Ratios (SMRs). We used Poisson regression analysis to calculate relative risks of death by country, period of follow up and interval between cancer diagnosis and subsequent birth.Results: The overall 15-year cumulative mortality was 18.2% (95% CI: 13.3 – 20.7%) which is substantially higher than that of the background population (SMR 13.3, 95%CI: 10.4-16.9). Excess mortality risks remained constant over follow up time and were comparable between Sweden and Singapore. Mortality risks decreased significantly with increasing interval between diagnosis and subsequent birth.Conclusion: Despite being 'healthy mothers', women who give birth after a diagnosis of breast cancer have a substantially higher risk of death than the background population. This information may be useful in a woman's decision whether to have a(another) child after breast cancer. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 3173.