What Is Use Of Taking Norethisterone After Incomplete Abortion?

I had miscarriage which began 3 weeks ago. I passed a lot of tissue without intervention. 1 week ago all bleeding/cramping stopped but gestational sac remained. Dr has prescribed 2x5 day course of norethisterone with 3 day break between. This seems to be prescribed to stop bleeding but would have thought I needed bleeding encouraged to pass remaining tissue. Very confused as to how this medication will help. Will I start bleeding? Or not until after finished the course? Feel as though this process is never ending.