Hello dear, I understand your concern. In my opinion the brown discharge might not be associated with prontogest injection. The various causes for brown discharge like thyroid abnormalities,progesterone or HCG insufficiency,bleeding from cervix,abnormal pregnancy,unknown causes etc. Infact the prontogest injection are given to stop spotting or bleeding caused due to hormonal abnormalities. The raise of HCG is also apt. The above causes should be ruled out by physical examination,thyroid profile and ultrasound. Dont worry.As the brown discharge does not always suggests miscarriage. I suggest you to consult doctor and rule out the above causes by examination and necessary investigations. It will subside with apt treatment. Avoid stress and physical strain.Take good rest.Avoid intercourse. Continue with medication as prescribed by your doctor. Hope this helps. Best regards...Dr.Srilatha