PRESS RELEASEMarch 10, 2017

Pregnancy does not increase the risk of dying from breast cancer, study published in JAMA Oncology finds

  • March 10, 2017

March 9, 2017  |  Download Release


TORONTO, MARCH 9, 2017 – Pregnancy does not increase a woman’s risk of dying from breast cancer, Women’s College Hospital (WCH) and Institute for Clinical Evaluative Sciences (ICES) scientists have found in a new study published today in JAMA Oncology. This study is the largest study to date on the subject.

More women are having babies in their late 30s and early 40s, and in rare cases, they are diagnosed with breast cancer around the time of pregnancy. Some studies have suggested that pregnancy around the time of breast cancer diagnosis may increase the risk of death. The current study found that the five-year survival rates for women who were not pregnant and women who were pregnant around the time of breast cancer diagnosis were similar.

The study was led by Steven Narod, MD, FRCPC, PhD (hon), FRSC, Women’s College Hospital senior scientist, director of the familial breast cancer research unit and a Tier One Canada Research Chair in Breast Cancer.

Some doctors now recommend that women wait two years before becoming pregnant after they finish treatment for breast cancer. The new study suggests those women need not delay their pregnancy.

“We think that a pregnancy at the time of breast cancer does not pose a risk to the mother,” Dr. Narod said.

The study used administrative databases from ICES, incorporating data on age, cancer stage, treatment and survival of more than 7,500 breast cancer patients between the ages of 20 and 44 in Ontario between 2003 and 2014.

The study found the five-year overall survival was 87.5 per cent for women with no pregnancy, 82.1 per cent for women with pregnancy-associated breast cancer and 96.7 per cent for women who had pregnancy six months or more after diagnosis of breast cancer. The difference between pregnancy groups was not significant.

The researchers found the early age at diagnosis was associated with more aggressive breast cancers, but it was not the pregnancy that was the risk factor.

“We know that breast cancers in young women are more aggressive and have a higher risk of recurring,” Dr. Narod says. “Our work shows that we need more studies to understand why younger women fare worse, and how to help them recover from breast cancer.”




About Women’s College Hospital 

For more than 100 years Women’s College Hospital (WCH) has been developing revolutionary advances in healthcare. Today, WCH is a world leader in the health of women and Canada’s leading, academic ambulatory hospital. A champion of health equity, WCH advocates for the health of all women from diverse cultures and backgrounds and ensures their needs are reflected in the care they receive. It focuses on delivering innovative solutions that address Canada’s most pressing issues related to population health, patient experience and system costs. The WCH Institute for Health System Solutions and Virtual Care (WIHV) is developing new, scalable models of care that deliver improved outcomes for patients and sustainable solutions for the health system as a whole. 

For more information about how WCH is transforming patient care and leading health system solutions, visit

Fully affiliated with

A member of