French researchers have reported an association between drugs given to mothers undergoing fertility treatment and an increased risk of leukaemia in their children.
They found that the use of fertility drugs was associated with a 2.6-fold increased risk of children developing a common childhood cancer, acute lymphoblastic leukaemia (ALL), and a 2.3-fold increased risk of developing the rarer acute myeloid leukaemia.
However, the risk remains very small in absolute terms; according to Professor Simon Fishel, chief executive of Care Fertility, this would only raise the risk from about 1 in 2,000 to 1 in 1,000.
The study, presented at the Childhood Cancer 2012 conference in London, but yet to be published in a peer-reviewed journal, included 764 French children diagnosed with leukaemia and 1,681 without the disease. Researchers asked parents for details of any fertility problems and whether they had undergone fertility treatments.
According to lead researcher Dr Jéremié Rudant, of the Centre for Research in Epidemiology and Population Health at the INSERM research institute in France, previous studies had 'been small, and they focused on IVF or hormonal treatment'.
He continued: 'Our study was much larger and it's the first time that a specific increased risk linked to fertility drugs has been found'.
However, they found no increased risk of childhood leukaemia following either IVF or artificial insemination, despite the fact women undergoing such procedures would also have undergone fertility treatment.
Kenneth Campbell, clinical information officer at Leukaemia and Lymphoma Research, similarly urged caution: 'This research is a long way from proving that A causes B. There are several alternative explanations'.
The study also found a 50 percent increased risk of ALL in children whose parents had taken more than a year to become pregnant naturally. Campbell suggested the association could be related to underlying genetic factors associated with lower fertility, rather than fertility drugs.
Dr Rudant acknowledged that the study did not prove conclusively that fertility drugs caused childhood leukaemia.
'More research is now needed to investigate more closely the link between specific types of fertility drugs and what role the underlying causes of infertility may play in the potential development of childhood leukaemia', he said.