In the UK, 5,000 women of reproductive age are affected by breast cancer every year and of all cases diagnosed in women aged 30 or under, 10 to 20 per cent take place during pregnancy or in the first year after a birth.
Breast cancer in pregnant women is generally diagnosed later than usual because symptoms are obscured by expected changes to the body such as an increase in cup-size.
The new report has said chemotherapy could be safely given in the second and third trimesters of pregnancy and, in general, surgery was safe during any of the three trimesters. In most cases, radiotherapy only became necessary after the birth, and it was not considered a reason to deliver a baby early.
A study in The Lancet Oncology backed up the claims, saying children exposed to chemotherapy in the womb developed just as well as those born to healthy women.
Current guidelines from the Royal College of Obstetricians and Gynaecologists agree that breast cancer does not appear to worsen the prognosis for women diagnosed in pregnancy and that surgery, including mastectomy, can be considered in all trimesters.
While chemotherapy is not recommended in the first trimester because of a higher risk of harm to the baby, it is considered safe from the second trimester.