Women diagnosed with breast cancer during pregnancy or soon after are not more likely to die from the disease or have a recurrence than other women, a new study says.

However, researchers at the University of Texas M. D. Anderson Cancer Center said they were more likely to be diagnosed at a more advanced stage.

"Breast cancer in young women is a highly aggressive disease, and it's important that we study it in hopes of making a difference in terms of treatment," said study author Dr. Beth Beadle.

It's estimated that up to 3.8 percent of pregnancies are complicated by breast cancer -- known as pregnancy associated breast cancer, or PABC. About 10 percent of breast cancer patients under age 40 develop had PABC, the researchers said.

Dr. George Perkins said there may be more cases as women generally wait longer to have children.

The research team reviewed medical records of 652 patients who were under age 35 when diagnosed. They were treated from 1973 to 2006.

The 10 year survival rate for women with PABC was 64.6 percent; for women who weren't pregnant, it was 64.8 percent. The difference is not statistically significant, researchers said.

They found, however, that half of the women with PABC did not get treatment until after they had their babies.

The findings are published in the March 15 issue of the journal Cancer.