Women who survive cancer are more than a third less likely to conceive than other women, research suggests.
New data from more than 23,000 female cancer survivors in Scotland found a 38% reduction in conception compared to the general population.
All the women were diagnosed with cancer as children or when they were under the age of 39.
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The research, which has not yet been published in a medical journal, was presented at the European Society of Human Reproduction and Embryology (ESHRE) conference in Geneva.
Experts examined data for all types of cancer and found a detrimental effect on fertility across the board, but particularly in cervical, breast and leukaemia patients.
Cancer and its treatment is known to affect fertility in several ways, including chemotherapy and radiotherapy damaging the ovaries.
Radiotherapy may also affect parts of the brain which control reproduction.
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Professor Richard Anderson, from Queen's Medical Research Institute at the University of Edinburgh, who led the study, said: "This analysis provides the first robust, population-based evidence of the effect of cancer and its treatment on subsequent pregnancy across the full reproductive age range.
"The major impact on pregnancy after some common cancers highlights the need for enhanced strategies to preserve fertility in girls and young women."
The study looked at data for 23,201 female cancer survivors, who had 6,627 pregnancies.
Experts said almost 11,000 would have been expected in a comparable matched control group from the general population.
For women who had not been pregnant before their cancer diagnosis, 21% achieved a pregnancy after their diagnosis compared with 39% in a control group.
This means those women with cancer were about half as likely to fall pregnant for the first time as other women.
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The study also found women diagnosed later on (2005 to 2012) had better chances of pregnancy than those diagnosed earlier in the study (1981 to 1988).
Prof Anderson said: "Some women may have chosen not to have a pregnancy.
"Thus, while these results do show an expected reduction in the chance of pregnancy after chemotherapy and radiotherapy, having a pregnancy after cancer does involve a range of complex issues that we cannot address in this study."
He said that while egg and embryo freezing are considered standard practice, access to them is variable across the UK.
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Freezing ovarian tissue directly is still considered "experimental, although it is the only option for pre-pubertal girls," he said.
He said, where appropriate, "options for fertility preservation should be discussed with the patient and her family".
"Even for patients considered at low risk of infertility as a result of treatment, a fertility discussion is recommended before treatment begins."
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