Physical and mental health correlates of pregnancy following breast cancer.

Introduction: The safety of pregnancy after breast cancer is an important issue for many younger breast cancer survivors and their health care providers. Current research does not indicate that pregnancy negatively affects survival, but the 'healthy mother bias,' suggesting that survivors who go on to become pregnant are a self-selected healthier group based on their prognosis, has led to cautious interpretation of these findings. No studies have systematically evaluated the potential for this bias.

Methods: This nested case-control study includes 81 younger participants from the Women's Healthy Eating and Living (WHEL) study (N=3088). Our sample includes 27 cases who had children after breast cancer and 54 controls, matched on age and stage at diagnosis. We used hierarchical linear modeling to accommodate longitudinal data with individuals nested within matched sets (cases and controls). The primary aim was to evaluate the association between summary scores of health and childbearing after breast cancer. Covariates were added for adjustment and to improve model precision.

Results: Controlling for other variables in the model, physical health scores were not different between cases and controls (B=0.14, p=0.96). Mental health scores were marginally higher among cases (B=6.40, p=0.08), as compared with controls, a difference considered clinically significant.

Conclusion: This preliminary study did not find evidence of a healthy mother bias based on physical health. However, mental health was 6 points higher (p=0.08) among those who had children, indicating that the role of mental health needs evaluation in future research. Larger studies are needed to verify these findings.