The investigators followed the survivors for approximately 10 years after their cancer diagnosis. Without regard to estrogen receptor status, the researchers found no difference in disease-free survival between those who became pregnant and those who did not. In addition, no differences were noted between those who carried their pregnancies to term and those whose pregnancies were terminated. However, with respect to ER-negative breast cancer, the investigators found mortality risk was 42% lower among the women who became pregnant compared with those who did not become pregnant. Dr Lambertini speculated that pregnancy might actually offer protection for patients with ER-negative breast cancer through hormonal or immune system mechanisms.

Impact on Nursing Mothers

This study also explored the impact of breastfeeding. In a small cohort of 64 women, 25 reported having breastfed their babies. Although the data were limited, study results show that even after breast surgery, an ability to breastfeed their newborns is reasonable for these patients.

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“This is the largest study addressing the safety of pregnancy in patients with a history of ER-positive breast cancer,” the investigators noted. Their long-term follow-up data confirm that women of childbearing potential should not be discouraged from having a child. Pregnancy is safe for these survivors irrespective of ER status of their disease.

Bette Weinstein Kaplan is a medical writer based in Tenafly, New Jersey. 


1. Lambertini M, Kroman N, Ameye L, et al. Safety of pregnancy in patients (pts) with history of estrogen receptor positive (ER+) breast cancer (BC): long-term follow-up analysis from a multicenter study. J Clin Oncol. 2017;35(suppl):LBA10066.