Abstract
Aetiological fractions are often used as an indirect measure of morbidity and mortality related to a specific risk factor. Aetiological fractions previously used in Australia for cocaine-related antenatal haemorrhage and low birth weight newborns have relied on risk ratios calculated from US-based studies. As outlined in this paper, there are several differences in the use and prevalence of cocaine and its associated harms between the two nations. As such, it is recommended that any use of these aetiological fractions with Australian data should occur with caution.