Clomiphene is in a class of medications termed estrogen antagonists. It prevents estrogen from exerting its effect in different parts of the body, including the pituitary. Estrogen is the main hormone produced by developing eggs. Therefore, when a woman’s pituitary gland in her brain is unable to recognize the estrogen coming from her eggs, it interprets this as no eggs are being produced, and consequently sends a stronger hormonal signal to the ovary to produce eggs. This stronger signal usually is able to stimulate egg development in women who are not naturally ovulating, such as those with PCOS. It can also lead to superovulation, when a woman who naturally produces one egg per month is able to produce multiple eggs under the influence of Clomid. If a woman is taking Clomid, we typically require ultrasound evaluations during the Clomid therapy in order to insure appropriate egg development is occurring and there is no negative impact on the lining of the uterus.