Ovulation induction in polycystic ovary syndrome
Letrozole beats clomiphene here. The same drug comes last in unexplained infertility.
If you have polycystic ovary syndrome and are not ovulating, this is one of the clearer answers in fertility medicine.
750 women with PCOS were randomly assigned, double-blind, to letrozole or clomiphene for up to five cycles:
| Outcome | Letrozole | Clomiphene | Effect |
|---|---|---|---|
| Cumulative live birth | 103 of 374 (27.5%) | 72 of 376 (19.1%) | Rate ratio 1.44 (95% CI 1.10 to 1.87) |
| Ovulation per cycle | 61.7% | 48.3% | P<0.001 |
| Twin pregnancy | 3.4% | 7.4% | No significant difference |
| Pregnancy loss | 31.8% | 29.1% | No significant difference |
An absolute difference of 8.4 percentage points, or roughly twelve women treated with letrozole instead of clomiphene for one additional live birth.
For completeness rather than alarm: there were four major congenital anomalies in the letrozole group and one in the clomiphene group. That difference was not statistically significant (P = 0.65) and the trial was not designed to answer that question. The numbers are reported here because leaving them out of a consent document would be the wrong call.
Same drug, opposite conclusion, different diagnosis. If letrozole is offered to you, the question is what it is being offered for.