After a full-term pregnancy, a woman goes into labor on or near her due date and gives birth to a healthy baby.

Has never been pregnant or had a full-term pregnancy.

The largest reduction in risk, 72 percent, was among the most active women who had had at least one full-term pregnancy.

Never having been pregnant or completed a full-term pregnancy.

But a full-term pregnancy can deliver between 37 weeks and 42 weeks.

The new study included 5,341 women with full-term pregnancies at 14 hospitals around the country.

A full-term pregnancy would result in a birth in May.

It occurs most often in women older than 30 who have had a full-term pregnancy.

It is rare in women who have not had a full-term pregnancy.

The risk of breast cancer appears to be lower if a woman has her first full-term pregnancy before she is 20 years old.