NEW YORK (Reuters Health) - The incidence of pregnancy-associated breast cancers has increased in Sweden over time, in part due to delayed childbearing, according to a report in Obstetrics and Gynecology in September.

"Breast cancer coinciding with childbearing has been denoted the "ultimate challenge" by posing extremely difficult questions to the caregiver, the patient, and her family," Dr. Therese M. L. Andersson, of Karolinska Institute, Stockholm, told Reuters Health in an interview. "An increased awareness of pregnancy-associated breast cancer can improve the clinical management of these young breast cancer patients, for example by avoiding undue delays in diagnosis and treatment."

Using Swedish registry data from 1963-2002 regarding 16,620 women who developed breast cancer at childbearing ages, Dr. Andersson and her colleagues identified 1161 cases of pregnancy-associated breast cancer.

The overall incidence was 27.9 per 100,000 deliveries. The researchers observed that from 1963 to 2002, the incidence of pregnancy-associated breast cancer rose from 16.0 to 37.4 per 100,000 deliveries.

Only 27 cancers were identified during the first two trimesters.

The overall rate of diagnosis was 2.38 per 100,000 deliveries during pregnancy, 10.6 per 100,000 deliveries in the first year after delivery, and 15.0 per 100,000 deliveries in the second year, the researchers report.

"Fewer pregnancy-associated breast cancers than expected were diagnosed during pregnancy and the first 6 months after delivery," they said. Beyond that point, however, there were no differences between expected and observed numbers of cases.

They add, "Our findings of an increased incidence...over time can be explained partly be a temporal trend of postponed childbearing....Another possible explanation...is an overall increase in the incidence of breast cancer in Sweden."

"Our next step is to examine and compare the characteristics of pregnancy-associated breast cancer with breast cancer among women of the same age with no recent birth," Dr. Andersson said. "We also want to compare the survival of women with pregnancy-associated breast cancer with that in women of the same age with breast cancer with no recent birth."