Finding may offer new ways to predict odds for the disease, researchers say.

Women who were thin as young girls are at increased risk for breast cancer as they age compared to women who were larger in girlhood, a new study finds.

Researchers examined the link between childhood body size and tumor characteristics in over 2,800 Swedish breast cancer patients and a control group of more than 3,100 women without breast cancer.

"Our main finding was that a large body type at age seven years was associated with a decreased risk of postmenopausal breast cancer," said study author Jingmei Li in a press release.

Although a large body type in girls is strongly associated with other known risk factors for breast cancer, such as early menstruation, a high adult BMI and breast density, Li said, a large body type at age seven "remained a significant protective factor after adjustment for these other issues."

"It appears counterintuitive that a large body size during childhood can reduce breast cancer risk, because a large birth weight and a high adult BMI have been shown to otherwise elevate breast cancer risk. There remain unanswered questions on mechanisms driving this protective effect," Li said.

The findings may offer a new way to help determine a woman's breast cancer risk.

"Given the strength of the associations, and the ease of retrieval of information on childhood shape from old photographs, childhood body size is potentially useful for building breast cancer risk or prognosis models," Li and colleagues concluded.

The study appears April 15 in the journal Breast Cancer Research.