Pregnancy and Chemotherapy
For a long time, doctors did not give chemotherapy to pregnant women and women of child-bearing age who received chemotherapy were advised to take precautions against pregnancy. If a pregnant woman got cancer, the pregnancy was either terminated or early labor was induced. While this is still the accepted best practice for oncologists in most cases, there is some science indicating chemotherapy may not be as detrimental to fetal development as feared.
A small study presented at the European Multidisciplinary Cancer Congress found just that. The scientists examined women who received chemotherapy while pregnant. They looked at the effects of the drug on the baby’s heart and nervous system and general health. The researchers had complete data on fewer than a hundred children, but none of them were born with congenital heart defects. Many of the babies were delivered prematurely, although it is not clear that the chemotherapy was the only or main factor in causing early delivery.
The babies who were born at full term had normal health and cognitive development at age 18 months. While larger studies are needed, this is an indication that “the fear of chemotherapy should no longer be an indication to terminate a pregnancy” according to what one research told the press. The president of the European Cancer Organization was quoted as saying a “paradigm shift” may be in the works on this issue.
Chemotherapy agents crossing the placenta?
How big of a problem is this? Fewer than 0.1% of pregnant woman have cancer. According to the National Cancer Institute, breast cancer happens in one out of every 3000 pregnancies.
The old-time chemotherapy agent methotrexate, still widely used, is also used in medical abortions. It induces miscarriages. Chemotherapy drugs can cross the placenta, and the cytotoxic effects of cancer drugs would seem logically to be detrimental to fetuses, or at least embryos. Teratogenicity is listed as a potential side effect for some chemotherapy agents and there are case studies of babies being born with defects after chemotherapy. (However, a study in baboons showed the placenta blocked most of the chemotherapy from the fetus, so exposure was much lower than in the mother’s tissue. Further work is needed in this area, but people are excited about the possibilities.)
A review of chemotherapy administration to pregnant women found that after the first trimester of pregnancy there is not a substantial increased risk of malformations but there is increased risk of stillbirth and intrauterine growth restriction.
When pregnant women have been given methotrexate during the first trimester, the baby sometimes ends up with malformations similar to the aminopterin syndrome.
There is scant evidence on the safety of chemotherapy for women who are breast feeding and whether the chemotherapy drug passes through the milk to the baby. The immunosuppressive drug azathioprine has been shown to not show up in breast milk in significant concentrations.
This has not been shown for other chemotherapy drugs, and in general, doctors tell women who have recently given birth to not breast feed. The benefits of breast feeding for the baby do not outweigh the risk of exposure.
Further, if a woman has had cancer when pregnant, the placenta is examined for malignant cells when the baby is born.