Experts say they have found, for the first time, that it is safe for women with the most common form of breast cancer to become pregnant.
Those diagnosed with oestrogen receptor positive breast cancer — which accounts for 80% of cases — can become pregnant without worrying it will increase their chances of the disease returning, research suggests.
Previously, doctors have feared that pregnancy can boost levels of oestrogen in the body and cause the cancer to come back.
The new findings suggest it is safe for women to fall pregnant even within the first two years after diagnosis.
Furthermore, the study found that patients who become pregnant appear to survive longer than those who do not, although further research is needed. Oestrogen is a female sex hormone which stimulates some breast cancers to grow by triggering particular proteins in cancer cells.
In a previous study, Dr Hatem Azim Jr and colleagues performed a review of 14 trials which showed it was safe for breast cancer patients to conceive.