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Some birth control pills can increase the risk of breast cancer, according to new researchers.

New findings reveal that women who recently used birth control pills containing high-dose estrogen and other specific formulations were more likely to develop breast cancer compared to women using other birth control pills.

"Our results suggest that use of contemporary oral contraceptives [birth control pills] in the past year is associated with an increased breast cancer risk relative to never or former oral contraceptive use, and that this risk may vary by oral contraceptive formulation," researcher Elisabeth F. Beaber, PhD, MPH, a staff scientist in the Public Health Sciences Division of Fred Hutchinson Cancer Research Center in Seattle, Washington, said in a news release.

"Our results require confirmation and should be interpreted cautiously," added Beaber. "Breast cancer is rare among young women and there are numerous established health benefits associated with oral contraceptive use that must be considered. In addition, prior studies suggest that the increased risk associated with recent oral contraceptive use declines after stopping oral contraceptives."

The latest study, which involved 1,102 women diagnosed with breast cancer and 21,952 controls, revealed that recent oral birth control use increased breast cancer by 50 percent compared to never or former use.

Furthermore, women taking birth control pills containing high-dose estrogen were 2.7 times more likely and those taking moderate-dose estrogen were 1.6 times more likely to develop breast cancer.

Researchers also found that contraception containing ethynodiol diacetate increased the breast cancer risk by 2.6, and triphasic combination pills containing an average of 0.75 milligrams of norethindrone increased the risk by 3.1 times.

However, researchers noted that low-dose estrogen birth control pills did not appear to increase the risk of breast cancer.

The findings are published in the journal Cancer Research.