Having a baby after breast cancer does not negatively impact a woman's chance of surviving the disease. A new study shows that survival is no worse in younger women, those who had not been pregnant before, and those with hormone-receptor positive breast cancer.

Results presented today at the 38th meeting of ESHRE based on more than 5000 women provide evidence to support motherhood after diagnosis. Details will be outlined today by Professor Richard Anderson from the Medical Research Council Centre for Reproductive Health at the University of Edinburgh, Scotland.

Professor Anderson says the findings are reassuring for women who develop breast cancer and want to become mothers.

Many breast cancers are hormone-sensitive. Tumor cells are stimulated to grow by estrogen and progesterone in the body. During pregnancy, levels of these hormones increase. This has long raised concerns that having a baby after breast cancer diagnosis and treatment may increase the odds of the disease returning or of a reduction in a woman's survival chances.

There is a growing need for data to establish if certain patients are likely to be affected. The average age of childbearing continues to increase so a large number of patients will not have had children when diagnosed.

The primary aim of this study was to establish if a live birth after breast cancer affected the survival chances of women. Professor Anderson and colleagues also analyzed factors influencing this (ie, tumor stage, previous pregnancy, and age at diagnosis).

Patient information from the Scottish Cancer Registry and national maternity databases was used to identify 5,181 women with a breast cancer diagnosis. All were less than 40 years old and diagnosed between 1981 and 2017. Pregnancies were included up to the end of 2018, and survival also analyzed up to that date.

Data were analyzed on 290 women who had a live birth after breast cancer diagnosis. For these women, results showed that their overall survival was higher compared with those who didn't have a birth after breast cancer diagnosis.

Survival was higher in those who had a first-time pregnancy after having breast cancer; women who had been pregnant before having breast cancer showed similar survival with or without a subsequent birth. A younger age at diagnosis with subsequent motherhood was also associated with increased survival, and all age groups showed increased or similar survival compared to women who did not have a baby after diagnosis.

In addition, most women who had a baby after diagnosis did so within five years. These women also showed increased survival compared to those who did not give birth after diagnosis.