Among women receiving treatment for unexplained infertility, taking the ovarian stimulating agent letrozole resulted in a significantly lower rate of multiple gestations compared with the standard therapy gonadotropin but not the standard therapy clomiphene citrate (Diamond MP et al. N Engl J Med. 2015;373:1230-1240).
Nine hundred women aged 18 to 40 years were randomly assigned to receive ovarian stimulation (up to 4 cycles) with gonadotropin, clomiphene, or letrozole, followed by intrauterine insemination. The women had regular menses, a normal uterine cavity with at least 1 fallopian tube, and a male partner with a sperm count of at least 5 million per mL.
Anita Slomski. Letrozole Therapy for Unexplained Infertility. JAMA. 2015;314(20):2122. doi:10.1001/jama.2015.15712