CHICAGO (AP) — A study gives reassuring news for breast cancer survivors who want to have children. Those who later became pregnant were no more likely to have their cancer come back than those who did not have a baby.

It's a big issue — the average age of moms has been rising in the United States, and more women are being diagnosed with breast cancer in their childbearing years. About 11 percent of new breast cancer cases in the U.S. are in women under 45.

The study, done in Europe, is the largest so far on women whose cancers were fueled by hormones, which rise in pregnancy and theoretically...