Infants from both groups experienced congenital problems, most of which were related to premature birth.

"We were surprised about the number of congenital malformations," Loibl said. "It is about 1 to 3 percent in the general population, but was higher in this cohort."

Although the study was primarily focused on the infant outcomes, the researchers also looked at the treatment effects on the women and found that the median overall disease-free survival of the mothers was 27 months and median overall survival was 55 months.

Based on these results Loibl said she would advise her pregnant cancer patients to "continue the pregnancy and start with a treatment as closely as possible to standard recommendations for nonpregnant women." In addition, it is critical that a multidisciplinary team in close collaboration with an obstetrician, prenatal care specialist and a neonatologist treat the pregnant woman with breast cancer.

Source: CTRC-AACR San Antonio Breast Cancer Symposium