Hallow Dear, Susten will be useful only if you have conceived and due to corpus luteum deficiency, there is Progesterone deficiency which cannot sustain the pregnancy. So before you take Susten, you will have to confirm that you have ovulated and had sexual relations on and around the day of ovulation. After conception, Susten will definitely help continuation of pregnancy. However, if there is no conception, your menses will be delayed till you continue to take these pills. After you discontinue the pills, you would get withdrawal bleeding within 4-7 days. It would not cause any irregularities in your menstrual cycles. Instead, I would advise you following: 1. First get confirmed that you ovulate (by ultrasonography). 2. Have sexual relations on and around the day of ovulation. 3. Take Inj. hCG on the day when your one of the follicle is around 18 mm size. It will cause the ovulation and support the corpus luteum also. If the conception has occurred, the pregnancy will continue, else, you will get menses after 10 days. Take only Gynaecologist s opinion. I hope this helps you. Dr. Nishikant Shrotri