(HealthDay News) — Use of letrozole (Femara) may reduce a couple’s risk for having a pregnancy with multiple embryos — but it might also slightly lower their chances of a live birth, a new clinical trial suggests. 

The study was published in the New England Journal of Medicine.

Michael Diamond, MD, professor and chair of the department of obstetrics and gynecology at Georgia Regents University in Augusta, and colleagues randomly assigned 900 women to undergo ovarian stimulation (for up to four treatment cycles) with either clomiphene, gonadotropin or letrozole.

Continue Reading

In the end, 32% of women on gonadotropin gave birth vs. 23% of women on clomiphene and 19% of those on letrozole. However, the difference between the clomiphene and letrozole groups was not statistically significant. 

Gonadotropin led to a higher birth rate, but it also raised couples’ odds of having twins or triplets. Eight percent of women on the drug had twins, and 2% had triplets, the research revealed. One percent of women on clomiphene had twins, as did 3% of those taking letrozole. None of the women on either clomiphene or letrozole had triplets.

“In women with unexplained infertility, ovarian stimulation with letrozole resulted in a significantly lower frequency of multiple gestation but also a lower frequency of live birth, as compared with gonadotropin but not as compared with clomiphene,” the researchers wrote.


  1. Diamond MP, Legro RS, Coutifaris C, et al. Letrozole, Gonadotropin, or Clomiphene for Unexplained Infertility. N Engl J Med. 2015;373:1230-1240.