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Use of letrozole results in reduced rates of clinical pregnancy, live birth

Compared with traditional therapies for ovarian stimulation, letrozole resulted in significantly lower rates of live birth and clinical pregnancy, according to findings published in The New England Journal of Medicine.

Michael P. Diamond, MD, Department of Obstetrics and Gynecology, Georgia Regents University, and colleagues also reported letrozole did not significantly reduce the rate of multiple gestation compared with standard therapies.

The researchers conducted a multicenter, randomized trial of 746 women with unexplained infertility, who were randomly assigned to gonadotropin, clomiphene or letrozole for ovarian stimulation.

Michael P. Diamond

Results showed that, with gonadotropin, clomiphene or letrozole, the rates of clinical pregnancies were 35.5%, 29.3% and 22.4%, respectively, and the rates of live birth were 32.2%, 23.3% and 18.7%, respectively. Additionally, the multiple gestation rate when using letrozole was similar to the rate when using gonadotropin or clomiphene (22%; P=0.15) or clomiphene alone (9%; P=0.44).

"In this large study, letrozole was not associated with increased risks of serious adverse maternal, fetal, or neonatal outcomes, as compared with the risks in the gonadotropin and clomiphene groups combined," Diamond and colleagues wrote. "Longer-term follow-up of these infants is ongoing. Although data about the risk of congenital anomalies after the use of an aromatase inhibitor have been limited, the frequency of congenital anomalies in our trial after treatment with letrozole (3.6%) did not differ significantly from the frequency after treatment with gonadotropin (3.1%) or clomiphene (4.3%)." – by Chelsea Frajerman Pardes

Disclosures: Diamond reports grant support from the NICHD during the conduct of the study; grant support from EMD Serono, AbbVie, and Bayer, and other support from Advanced Reproductive Care outside the submitted work. Please see the full study for a list of all other authors' relevant financial disclosures.