Women who had cancer when they were children have a good chance of being able to conceive, however male childhood cancer survivors are less likely to go on to have children, one of the largest studies of its kind has found.

Currently, over 80% of children with cancer can expect to survive into adulthood and for many, whether they can have families of their own is a major issue.

As the effects of radiotherapy in children can be severe, childhood cancers are more likely to be treated nowadays with intensive chemotherapies, however previous studies have found that fertility can be adversely affected by some types of chemotherapy.

However, little research has been carried out into the effects on pregnancy from newer types of chemotherapy in childhood cancer survivors.

US researchers decided to look into this further. They analysed data from a study which tracked people who were diagnosed with the most common types of childhood cancer between 1970 and 1999.

The study assessed the impact of different doses of 14 commonly used chemotherapy drugs on pregnancy and live birth rates among almost 11,000 survivors, compared with more than 3,900 siblings.

The researchers found that by the age of 45, 70% of the female cancer survivors had become pregnant, compared to over 80% of their siblings. However, for male cancer survivors, this figure was 50%.

Among male survivors, the chance of becoming a father appeared to decrease the more they were exposed to chemotherapy that contained high doses of commonly used alkylating drugs. This applied to several different types of chemotherapy.

The findings are consistent with previous studies which have found that men who have been exposed to these drugs have a lower sperm count and reduced testicular volume.

Among female survivors, just two drugs appeared to be directly linked with a reduced risk of pregnancy.

While female survivors were overall less likely than their siblings to become pregnant, this effect was still much smaller than that seen in male survivors.

However, the researchers noted that the ability to conceive appeared to reduce more if the women were aged 30 or older. They suggested that this is because exposure to chemotherapy may accelerate the natural depletion of eggs, leading to earlier menopause.

"We think these results will be encouraging for most women who were treated with chemotherapy in childhood," commented Dr Eric Chow of the Fred Hutchinson Cancer Research Center in Seattle.

However, he said that doctors ‘still need to do a better job discussing fertility and fertility preservation options with patients and their families' before starting treatment for cancer.

Details of these findings are published in the journal, The Lancet Oncology.