Use of Chemotherapy during Pregnancy – Is It Safe?
By Ng Hui Cheng
Senior Oncology Pharmacist, NCC
When a pregnant woman is diagnosed with cancer, and although chemotherapy proves to be a life-saving option for the mother, it will always be a dilemma as to whether the treatment will threaten the life of the growing foetus. One may think that if this is a concern, just delay the chemotherapy until after delivery; however this may not always be possible depending on the type of cancer and the stage at diagnosis. It has been reported that cancer develops in approximately one per 1000 pregnant women and the incidence is expected to rise as women delay childbearing until a later age.
Whether a chemotherapeutic drug will cause harm to the fetus depends on the timing of exposure, the dose, and the characteristics affecting placental transfer. The use of chemotherapy significantly impacts the pregnancy; on the contrary, pregnancy may also affect the treatment options available to patients with cancer. Sometimes, the cancer itself can contribute to the risk of foetal loss. Here are some examples of chemotherapeutic drugs given during the first trimester and their estimated risk of fetal malformation:
Drug
|
Risk
|
Chlorambucil
Nitrogen mustard
5-fluorouracil
Methotrexate
Cyclophosphamide
Cytarabine
Busulfan
|
1:2
1:3
1:3
1:4
1:6
1:8
1:9 |
In the first trimester, the foetus starts to develop major organs, such as the heart, neural tube, arms and legs, ears, palate and lips. Generally, the use of chemotherapy is not recommended in this trimester, unless it is absolutely crucial for the survival of the mother, as this increases the risk of spontaneous abortion, malformations, and death of the foetus.
On the other hand, chemotherapy seems to be safe during the second and third trimesters. Patients are also advised to avoid breast-feeding when undergoing chemotherapy. It is suggested that delivery should be delayed by 2 to 3 weeks after chemotherapy to allow the bone marrow to recover.
The above general recommendations have been reported in various literatures where immediate treatment of the pregnant woman with chemotherapy proves mandatory for survival. However, bear in mind that a majority of these findings came from reports of physicians who had treated their pregnant patients and that it is impossible for any randomized trials to be designed to investigate the safety of chemotherapy in pregnant women.
In view of the limited data available, the long-term health of exposed children has not been adequately studied and this remains a concern. The patient, together with her family, should discuss with the physician to decide what is best for the mother as well as the foetus.
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