New research offers reassurance to women worried about whether getting pregnant after cancer treatment might worsen their prognosis.

The study by Norwegian scientists, presented at the European Cancer Conference (ECCO 14) in Barcelona, found that for almost all types of cancer, the survival of women who are diagnosed during pregnancy or who became pregnant after being treated for the disease is no different from that of other female cancer patients.

"The only exception was for breast cancer diagnosed during lactation, where women were 1.9 times more likely than normal to die from their cancer," said Dr. Hanne Stensheim, a research fellow at the Norwegian Cancer Registry in Oslo, Norway, who led the study. "We think this is mainly based on greater delay in diagnosis, rather than any influence of the lactation process itself. It may be more difficult to diagnose breast cancer during lactation because many women get lumps due to mastitis and because normal physiological changes in the breast might mask suspicious developments."

Breast cancer is one of the most common cancers diagnosed during pregnancy, but pregnancy-related breast cancer is relatively rare. Studies have suggested that between 0.2 percent and 3.8 percent of breast cancers diagnosed in women under age 50 are detected during pregnancy or the postpartum period.