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Friday, 30 March, 2001, 23:51 GMT 00:51 UK
IVF risk after cancer treatment
egg
A mature human egg: worries over chemotherapy
Supplying eggs for fertility treatment shortly after cancer treatment may increase the risk of pregnancy problems, according to a study.

Eggs retrieved from a woman who has been treated with a certain class of chemotherapy drug might be vulnerable to damage.

In humans, a woman carries a lifetime's eggs in the ovaries, the majority lying in a dormant state.

At any time, a number will be maturing - a process which takes a period of several months - until they are ready to be released during ovulation each month.

Animal experiments carried out in Israel and the UK suggest that the effects of certain drugs on eggs at a certain stage of maturation may be devastating.

Some female patients who are told they have cancer face the prospect of chemotherapy or radiotherapy rendering them infertile.

They have two options after diagnosis, either to have eggs retrieved for IVF before treatment starts, or, if delaying treatment is dangerous, to have eggs retrieved following initial, non-sterilising chemotherapy.

If it is proved that even the non-sterilising chemotherapy can damage eggs, then this could rule out this option for several months after the treatment.

Doctors at research centres in Israel, alongside others from the Univeristy of Leeds looked at the effects of one commonly-used non-sterilising drug, cylophosphamide, on eggs in mice.

The mice were given the drug, and mated between one and 12 weeks later - it takes only three weeks for eggs to mature in mice, compared to between six to 12 months in humans.

More miscarriages

There were fewer pregnancies in the mice whose egg follicles were mature when the chemotherapy was given.

There was also a significantly higher miscarriage rate and 10 times the number of malformed embyros.

The worst cases happened when the chemotherapy was given while the eggs were their earliest maturation stage.

This level of defects and miscarriages fell away as the interval between chemotherapy and mating increased.

While the scientific team are not claiming that the results would definitely be the same in humans, it was clear that more research was needed.

Dr Dror Meirow, from the Rabin Medical Centre, said: "This suggests that the effect of cyclophosphamide on eggs, and subsequently on future reproduction, is influenced by the stage of maturity the egg has reached at the time of treatment.

'Safety period'

"It is clear that early fertilisation post-chemotherapy can result in a high rate of pregnancy failure and malformation."

If further research confirmed that the effect could be the same in humans, he said it would be vital to define a "safety period" between the end of treatment and egg retrieval for IVF.

He said any foetuses carried by women who had been given this drug or similar drugs should be screened for genetic malformations.

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See also:

25 Jan 00 | Health
Frozen egg ban lifted
23 Sep 99 | Medical notes
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02 Oct 00 | Health
Fertility hope for cancer women
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