THURSDAY, Feb. 9 (HealthDay News) -- A new study finds that the babies of women who had chemotherapy while pregnant aren't at higher risk for a variety of medical disorders, a sign that the treatment should be safe for the fetus in most instances.

There's a caveat: babies born to pregnant women who had chemotherapy were more likely to be born prematurely, potentially putting them at risk for impaired brain development, which can cause problems with memory, thinking and learning skills.

Still, the findings are "very good news," said maternal-fetal medicine specialist Dr. Elyce Cardonick, who wrote a commentary accompanying the study.

"No pregnant woman likes to choose between treating themselves and protecting the baby," said Cardonick, who works at Cooper Medical School of Rowan University in Camden, N.J. "They don't have to choose. By making themselves healthy, they're helping the baby."

An estimated one in 1,000 pregnant women have cancer, Cardonick said. In some cases, doctors recommend that the women undergo abortions. But chemotherapy is an option.

Typically, doctors only treat the women outside the early stages of pregnancy and use older drugs that are "tried and true," Cardonick said.

Could chemotherapy harm the developing fetus? Previous research has suggested it won't, but researchers led by Dr. Frederic Amant, a gynecologic oncologist and assistant professor at Katholieke Universiteit in Leuven, Belgium, sought to understand whether the cancer treatment might affect babies after they are born.

In the new study, the researchers examined medical records and test results of 70 children whose pregnant mothers underwent chemotherapy. The children were followed for an average of 22 months and up to 18 years.

"The study is unique since this is the first time children were extensively examined over the long term," Amant said.

The investigators found that the children weren't at higher risk of heart, hearing or nervous system disorders, or general health and growth problems.

As to why the chemotherapy drugs do not reach the fetus and cause harm, Amant said the placenta acts like a filter, keeping most of the medications away from the fetus. Also, doctors avoid chemotherapy in the first trimester, when organs are in the early stages of development and especially vulnerable, Amant added.

The study is one of a series of articles about pregnant women and cancer published online Feb. 10 in The Lancet Oncology.

The other articles published in this issue report that:

• The current trend in medicine is to allow pregnancies to continue in women diagnosed with cervical or ovarian cancer. However, chemotherapy must not be used in the first eight weeks, and the pregnancies come with risks.
• Pregnant women with breast cancer can undergo both surgery and chemotherapy, all with the aim of a full-term pregnancy. The mother's disease outcome would not be improved by terminating the pregnancy.
• Blood cancer can cause complications in pregnant women, such as blood clots, that may lead to advice to terminate the pregnancy at an early stage to protect the health of the mother. But women in later stages of pregnancy may find it feasible to undergo cancer treatment while preserving the pregnancy.

More information

For more about pregnancy and cancer, visit the American Society of Clinical Oncology.