Cancer as a cause of abortions and stillbirths: the effect of these early deaths on the recognition of radiogenic leukaemias.

Data from the Oxford Survey have shown that childhood cancers are causes of in utero deaths which affect leukaemias more than solid tumours and difficult deliveries more than easy ones. As a result of these biases singletons give the impression of being more leukaemia-sensitive than twins. This is a false impression which affects other situations and makes it more difficult to detect the leukaemogenic effects of obstetric radiography in a prospective survey than in a case-history survey, and essential to look for these effects beyond the period affected by the in utero deaths.