Why would you have light bleed 5 days after an iui?

Several things: Bleeding post IUI can be caused by a friable, or cervix thats bleed easy, a small bleed behind the gestational sac, following intercourse, the loss of a twin and/or signs of an early miscarriage. If you have any bleeding, contact your doctor immediately. And remember, it may not be a bad sign. Probably would consider starting Progesterone to help quiet the uterus. Good luck.