Can letrozole help infertile PCOS patients become pregnant?

A study in The New England Journal of Medicine funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development suggests that letrozole may be more effective at helping women with polycystic ovary syndrome (PCOS) become pregnant than clomiphene.

Led by researchers from Penn State College of Medicine, the  double-blind, multicenter trial enrolled 750 women aged 18 to 40 with at least 1 patent fallopian tube, a normal uterine cavity and a male partner with a sperm concentration of at least 14 million/mL. The couples had to agree to engage in regular intercourse with the intent of conception. The women were randomized to receive letrozole or clomiphene for up to 5 treatment cycles and had visits to determine ovulation and pregnancy, as well as pregnancy tracking. Modified Rotterdam criteria were used to determine PCOS status.

Women in the letrozole group had more cumulative live births than those in the clomiphene group (103 of 374 [27.5%] vs 72 of 376 [19.1%], P=0.007; rate ratio for live birth, 1.44; 95% confidence interval, 1.10 to 1.87) with no significant differences in overall congenital anomalies. However, there were 4 major congenital anomalies in the letrozole group, while the clomiphene group only had 1 (P = 0.65). Letrozole was also associated with a higher cumulative ovulation rate than clomiphene (834 of 1352 treatment cycles [61.7%] vs 688 of 1425 treatment cycles [48.3%], P<0.001). In addition, no significant difference between the groups was seen in pregnancy loss (49 of 154 pregnancies in the letrozole group [31.8%] and 30 of 103 pregnancies in the clomiphene group [29.1%]) or twin pregnancy (3.4% and 7.4%, respectively). Letrozole was associated with a higher incidence of fatigue and dizziness whereas clomiphene was associated with a higher incidence of hot flushes. The rates of other adverse events were similar in the two groups.

The investigators concluded that when compared to clomiphene, letrozole was associated with a higher rate of live birth and ovulation in infertile women with PCOS.

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