complication
unfavourable evolution of a disease, a health condition or a therapy, which may adversely affect the prognosis or outcome
en-GB/ˌkɒmplɪˈkeɪʃn/
en-US/ˌkɑmpləˈkeɪʃən/
unfavourable evolution of a disease, a health condition or a therapy, which may adversely affect the prognosis or outcome