(HealthDay)—Many teen girls with leukemia aren't checked for pregnancy before they receive chemotherapy drugs that can cause birth defects, a new study finds.

Despite the risk of birth defects posed by these drugs, there are no standardized guidelines for pregnancy screening in teen cancer , the researchers said.

"Since nearly all chemotherapy agents used for childhood/adolescent acute leukemia can cause potential harm to a developing fetus, our findings indicate a need for standardized pregnancy screening practices for adolescent patients being treated for cancer," said study author Dr. Pooja Rao. She was with a team from the University of Pennsylvania School of Medicine and Children's Hospital of Philadelphia when the study was conducted.

The researchers analyzed data from 10- to 18-year-old girls in the United States diagnosed with (ALL) or (AML) between 1999 and 2011. Leukemia is a cancer that starts in early blood-forming cells found in the bone marrow, the soft inner part of certain bones.

The study compared the leukemia patients with cancer-free girls of the same age who underwent CT scans of the abdomen or pelvis in emergency departments over the same time period. In emergency medicine, pregnancy screening protocols exist for teen girls prior to receiving medical imaging tests that use radiation.

Pregnancy screenings were conducted on 35 percent of ALL patients, 64 percent of AML patients and 58 percent of emergency department patients. There was wide variation in pregnancy screening patterns among different hospitals, the investigators found.

The study was published online Sept. 12 in the journal Cancer.

"We found that adolescent girls are not adequately screened for pregnancy prior to receiving chemotherapy or CT scans that could harm a developing fetus. Adolescents with ALL, the most common childhood cancer, had the lowest rates of pregnancy screening of the patients we studied," Rao said in a journal news release.

The findings may indicate a reluctance on the part of childhood cancer specialists (pediatric oncologists) to discuss with teen patients, Rao suggested.

"While sexual health discussions and education may traditionally be thought to be the responsibility of the patient's primary care provider, adolescents with cancer will often see their oncologist frequently over the course of their treatment, and afterwards," she said.

"Oncologists therefore are well-positioned to initiate discussions about sexual health with their patients," Rao said.

Although rare overall in childhood, accounts for almost one out of three cancers in children and teens, according to the American Cancer Society.

More information: The U.S. National Cancer Institute has more on leukemia.

Journal information: Cancer