This suggests current recommendations for premenopausal women to wait two years after their diagnosis may be unnecessary for women younger than 45 who have localised disease.
The two-year guide is based on anecdotal evidence that considers the risk of early occurrence and the need to allow adjuvant therapy to be completed. It is likely to still stand for women with systemic disease at diagnosis or who are still receiving treatment.
The latest study involved 2,539 women aged 15-44 who were diagnosed with breast cancer between 1982 and 2000. Five per cent had at least one subsequent pregnancy by the end of 2003.
Of the 123 women who became pregnant, 16 per cent conceived within six months of diagnosis and 54 per cent within two years. Forty-four per cent went on to have a live birth.
Providing chemotherapy was not given at the time of conception or in the first trimester of pregnancy, no short- or long-term health effects were noted among children of women who conceived after diagnosis, said researchers.
Among women who conceived after their diagnosis, five-year survival was 92 per cent and 10-year survival was 86 per cent.