MONDAY, Feb. 9 (HealthDay News) -- Developing breast cancer during or within a year of pregnancy may not -- as previously thought -- affect the severity of the disease or the chance of surviving it, according to new research.

Of 652 women, 35 or younger, with breast cancer participating in a University of Texas M.D. Anderson Cancer Center study, about 16 percent had the rare pregnancy-associated breast cancer (PABC).

Rates of cancer recurrence, spread and survival after 10 years were virtually the same among women with PABC and the other women with breast cancer.

The finding contradicts previous studies that had suggested that women with PABC fared worse than non-pregnant breast cancer patients.

Though researchers noted that pregnancy often causes a delay in diagnosing as well as treating breast cancer, they found that women improved their chances of survival by receiving treatment during pregnancy rather than waiting until after giving birth.

"Primary care and reproductive physicians should be aggressive in the work-up of breast symptoms in the pregnant population to expedite diagnosis and allow multidisciplinary treatment," the authors wrote in their report, published in the March 15 issue of Cancer . "Balancing the health of mother and child is paramount; new evidence suggests that both can be prioritized and successful outcomes managed for both."

Breast cancer affects fewer than 4 percent of all pregnancies and rarely occurs in women younger than 40.

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