Cancer treatment in pregnancy may affect fertility of unborn baby girls

Chemotherapy treatment during pregnancy may affect the future fertility of unborn baby girls, a new study suggests.

Around one in 1000 pregnant women are diagnosed with cancer. Doctors and patients have to make difficult decisions to try and save the lives of both mother and baby. Chemotherapy administration during the first trimester of pregnancy (up to 12-14 weeks) is often avoided, as it is associated with increased risk of congenital deformity and high risk of spontaneous abortion.

Chemotherapy treatment during pregnancy

During the second and third trimesters of pregnancy (from 4-9 months) chemotherapy treatment has been considered to be relatively safe for the developing foetus, with several studies showing no birth defects in infants born to women who received chemotherapy at that time. A drug that is commonly used is Etoposide, which can be used to treat several types of cancer and works by blocking an enzyme, which is necessary for cancer cells to divide and grow intotwo new cells.

However, little is known about the possible long-term detrimental effects of chemotherapy treatment on the reproductive system of unborn baby girls.The reproductive lifespan of a female is determined before birth, during the second and third trimesters of pregnancy, when female germ cells form structures called follicles that determine how many eggs a woman will be able to release in her lifetime. Scientists at the University of Edinburgh therefore set out to examine the effect of treatment with a commonly used cancer drug, Etoposide, on germ cells in the developing ovary by studying the development of mouse ovary tissue grown in the laboratory.

Etoposide exposure wiped out almost all germ cells

At around 17 weeks of gestation, foetal follicle development starts and continues into the later stages of pregnancy.

The results of the new study indicated that 90 percent of germ cells were eliminated when treatment commenced prior to follicle development. However, when treatment took place after the follicles had developed, no significant adverse effects were observed.

The study, published in BMC Cancer, also suggests that any genetic damage to germ cells during foetal development could then be passed on to subsequent generations, called the "grand-maternal" effect.

The authors write that the findings are cause for concern, especially since etoposide is already prescribed to pregnant women, and the drug may potentially have a similar effect in human foetal ovaries to mice.

Lead researcher Professor Norah Spears, of the University’s Centre for Integrative Physiology, said: “If the results we have seen in these mouse studies are replicated in human tissue, it could mean that girls born to mums who are taking etoposide during pregnancy have a reduced fertility window.”

The potential for adverse effects on foetal ovarian development when etoposide is used in pregnant women during the second or third trimesters, at which point pre-follicular female germ cells are sensitive to the detrimental effects of this compound - may not become apparent until many years later, the study concludes.

Undesirable side-effects of medication. Full medical glossary
Abnormal, uncontrolled cell division resulting in a malignant tumour that may invade surrounding tissues or spread to distant parts of the body. Full medical glossary
The basic unit of all living organisms. Full medical glossary
The use of chemical substances to treat disease, particularly cancer. Full medical glossary
Any condition present since birth. Full medical glossary
A protein that speeds up chemical reactions in the body without being used up itself. Full medical glossary
The basic unit of genetic material carried on chromosomes. Full medical glossary
Relating to the genes, the basic units of genetic material. Full medical glossary
In pregnancy, the time from conception to birth. Full medical glossary
relating to the ovaries Full medical glossary
Female reproductive organs situated one on either side of the uterus (womb). They produce egg cells (ova) and hormones in a monthly cycle. Full medical glossary
the period from conception to birth Full medical glossary
A group of cells with a similar structure and a specialised function. Full medical glossary
A period of three months often used to describe the stage of pregnancy, where there are three - first, second and third trimesters. Full medical glossary