Question:

What is the success rate of using Clomid for infertility? Is there a risk of multiple births?

Answer:

Clomid is the brand name of the drug clomiphene, which is used to stimulate the ovary to release an egg. It is used to treat women who are infertile because they have no ovulation or infrequent ovulation. Clomiphene stimulates molecules inside of cells that are normally stimulated by the hormone estrogen. One important function of these molecules is controlling the steps that lead to ovulation.

Infertility has many causes. Failure of ovulation is one of the most common. It is also one of the most successfully treated. If failure to ovulate is the only problem a couple faces, the use of clomiphene has about a 40% success rate for achieving pregnancy.

Side effects can occur with clomiphene. The most common side effects are multiple pregnancy and hot flashes. The rate of twin pregnancy with clomiphene is reported between 7% and 9%. Triplet and higher multiple pregnancy occurs in less than 1% of clomiphene induced pregnancies.

An uncommon but potentially serious complication from clomiphene and other "fertility drugs" is swelling of the ovaries. We call this ovarian hyperstimulation. The ovaries can leak fluid into the belly.

Clomiphene alone rarely causes ovarian hyperstimulation. It occurs more often after an injection of human chorionic gonadotropin is given to trigger the release of eggs from the ovary.

— Joan Bengtson, M.D.
Assistant professor of Obstetrics, Gynecology and Reproductive Biology, Harvard Medical School
Department of Obstetrics, Gynecology and Reproduction, Brigham and Women's Hospital