Hello, Susten is brand name of progesterone drug. Susten is usually prescribed in leuteal phase deficiency ie. progesterone deficiency. Progesterone deficiency is usually suspected in pregnant females those who have bleeding or spotting in early Pregnancy. Thus Sustan is given for you. Progesterone have following benifits in pregnancy. 1. Makes the endometrium develop 2. Maintains the functions of the placenta 3. Stops the uterus making spontaneous movements 4. Stimulates the growth of breast tissue 5. Prevents lactation until after the birth (with estrogen 6. Strengthens the mucus plug covering the cervix to prevent infection 7. Strengthens the pelvic walls in preparation for labour 8. Stops the uterus from contracting. Your doctor advised to stop after 7 months,because uterus may start contract after 7 months to expel the fetus. This results in birth of child. There is No major side effect for sustan at this dose. Hope this helps. Please write back for further queries. Wishing you good health.