Letrozole is a drug that is called an aromatase enzyme inhibitor, meaning that it blocks the production of estrogen in the ovary. This leads to increased secretion of FSH from the pituitary which in turn stimulates the ovary to develop a follicle for ovulation. Like clomid, it is used to induce ovulation in women who don’t ovulate on their own.
Clomid may also be used in combination with IUI for unexplained infertility to increase the pregnancy rate above what it would be if you try on your own. In someone who doesn’t react well to clomid, letrozole may be a reasonable alternative.
Letrozole is used in women with breast cancer to lower their estrogen levels which in turn reduces the incidence of recurrence of the cancer. Unlike clomid, it is not approved for use in infertility, but is often used “off-label” by fertility doctors. Pregnancy rates with letrozole appear to be similar to those with clomid, but they are no better, so usually clomid is used unless the patient is unresponsive or has a bad reaction to clomid (like you).
Some concerns have been raised because letrozole may cause birth defects if administered inadvertently during early pregnancy. However, a large study of 911 newborns conceived using letrozole for ovulation induction showed no difference in rates of congenital malformations. In addition, letrozole is eliminated from the body more quickly than clomid and should be gone by the time of embryo implantation which should should prevent any effect on a developing embryo when it is used prior to ovulation.
The bottom line is that letrozole probably shouldn’t be used when clomid can because it is no more effective and concerns about its safety have been raised. But in cases where clomid can’t be used, it may be used and is probably safe based on the information above.
Best of luck!
Dr Barry Witt
Hi All-
We just got back from visiting our fertility specialist. After figuring out that everything is fine with my husband, and that everything physically seems alright with me, he has recommended we do a few months of a Letrozole/Femara with Artificial Insemination combo. He suggested this route because of a bad reaction I had to Clomid when taking that previously. During our conversation, our doctor did tell us about the potential for increased birth defects (from a Canadian study of the drug) associated with Femara. Before signing on for this course, my husband and I wanted to do some more research. Does anyone have any advice or information they think we should know?
We appreciate any information.
Thanks!
