Hi Darren, Duphaston is the trade name for Dydrogesterone, which is progesterone without estrogen.It is orally active and works directly on estrogen primed uterus. (Progesterone and Estrogen are both female hormones. Estrogens are dominantly secreted before ovulation and Progesterone are secreted after ovulation.). Duphaston usually supports pregnancy and is given in pregnant women if there is any threat of abortion (such as if the patient has had bleeding in the first trimester). It is also given in case of irregular periods as a progesterone challenge. If everything else is fine, most the times, periods normalize and ovulation occurs. That being said, there are several ways how Duphaston is conducive to pregnancy occurrence and continuation and there could be several reasons why you have been advised the medicine. We would need more details around your gynecological, obstetrical and medical history and history of present complaints to advise further. Hence, it may be best for you to confirm the days with your infertility specialist. Additional information: Fertomid and Clomid are trade names for clomiphene which is a drug used for fertility treatment. It induces ovulation. There are chances that you conceive in the first month of treatment but it wouldn t be a surprise if you may need to repeat. Hope that helps. Take care and all the best with your treatment!