This depends on what life stage you are in! Read on for details during various life stages.
Menstruation or Interim Bleeding: Steaming is not done when you are fresh bleeding or spotting. When you are bleeding or spotting the uterine artery is opened. The warmth, herbs, and circulation increase from the steam can trigger cases excessive or flood bleeding in small amounts of cases if you steam while you are bleeding.
If you are having brown spotting it is okay to steam.