Australia has a slightly different pregnancy category system[4] from the United States – notably the subdivision of Category B. (For drugs in B1, B2 and B3 categories, human data are lacking or inadequate. Subcategorisation is based on animal data, and allocation of a B category does not imply greater safety than C category).[5] The system, as outlined below, was developed by medical and scientific experts based on available evidence of risks associated with taking particular medicines while pregnant.