Q: I am 5 months pregnant with my first child and have found that my boyfriend's family has a few cases of terminal childhood leukaemia. The first being his elder brother and the second his cousin's daughter. There is no history of leukaemia in my family, although my mother was diagnosed with ovarian cancer two years ago, but overcame it and is now in remission. With their second child, my boyfriend's cousin has banked the placenta blood from the birth in case of necessity. Are there any possible risks that we should be aware of? Should we consider blood banking too?

A:One fundamental concept in cancer biology is that cancer is caused by mutations in normal genes, independent of the cause of the mutation. A mutation is a permanent structural alteration in the DNA and is passed on to the progeny. Most often such changes are harmless or they may have a deleterious effect on the organism. They are thought to be random chance events and can be caused by a variety of agents like radiation and chemicals. Leukaemia is thought to be a multistep process in which a susceptible stem cell is exposed to inductive agents at multiple stages. Familial leukaemia may occur in the context of a clinical syndrome in which the leukaemia is a component of the overall disease or it may be an isolated predisposition. Syndromes associated with an increased leukaemia risk include genetic abnormalities like trisomy 8 & trisomy 21 (Down syndrome) and conditions such as Bloom’s syndrome, Fanconi’s anaemia, ataxia telangiectasia, neurofibromatosis, Wiskott-Aldrich syndrome etc. There are instances of rare familial leukaemia that are not associated with defined syndrome but show some pattern of inheritance (autosomal recessive or autosomal dominant) in the families. For all types of acute myeloid leukaemia there is a three-fold increase in the incidence of leukaemia in first-degree relatives of patients while it is double for acute lymphoblastic leukaemia. The molecular mechanisms for a genetic predisposition and the familial occurrence of acute leukaemia are still a mystery. Despite all this knowledge, most patients of leukaemia show no evidence of any of these risk factors and most often the underlying cause is not known. One can bank a baby’s stem cells for future use in siblings but the likelihood of its use appears slim.