Fetal risk from chemo highest in first trimester: data on 619 cases: congenital malformations seen in 19.1%.(News)

LOS ANGELES -- Chemotherapy during pregnancy may not lead to an elevated rate of fetal malformations if it is given after the first trimester, according to a report on the first 619 cases entered into the federal Registry of Pregnancies Exposed to Chemotherapeutic Agents.

Among 271 fetuses exposed to chemotherapeutic agents during the first trimester, 19.1% were born with congenital malformations, compared with 5.5% of 348 fetuses exposed to chemotherapy during the second or third trimesters, said senior genetic counselor Susan Hassed of the University of Oklahoma Health Sciences Center, Oklahoma City.

The expected rate of malformations in the general population is 5%, she said at the annual meeting of the American Society of Human Genetics.

Ms. Hassed and medical geneticist Dr. John J. Mulvihill said that the federal registry has collected data since 1984 on chemotherapy exposed pregnancies described in the literature or submitted by medical professionals. Established at the National Cancer Institute, the registry moved to the University of Oklahoma in 1998 and is currently seeking wider reporting by medical professionals.

The majority of cases included thus far involves mothers treated for cancer during pregnancy, but in 59 instances, the drugs were received by pregnant transplant or autoimmune disease patients, or during attempted abortions. Annually, an estimated 3,400 U.S. women become pregnant and develop cancer during the same year.

"Pregnancy is a time of rapid cell proliferation. Many chemotherapeutic agents are specifically designed to stop rapid cell proliferation; therefore, it is reasonable to predict that cancer drugs would harm a developing fetus," Ms. Hassed said.