Asalaamu Alaikum, jazakallahu khayr for the question. For frequant miscarriages it is a possibility but we should know that whatever happens whether it be sihr or not will only happen by the will of Allah and when a soul has reached its appointd time then it will be taken and that also goes for the case of a still birth or a miscarriaged child. If one needs diagnosis because of certain effects one may have of sihr then one should go to a qualified Raqi or scholar.
If you want to know more about Sihr and its possible affects then you can read this brilliant PDF on the topic: