Letrozole and gonadotropins versus luteal estradiol and gonadotropin-releasing hormone antagonist protocol in women with a prior low response to ovarian stimulation.

Objective: To compare in vitro fertilization outcomes after ovarian stimulation using letrozole/antagonist (LA) versus luteal-phase estradiol (E(2))/gonadotropin-releasing hormone (GnRH) antagonist (LPG) in poor responders.

Design: Retrospective study.

Setting: Academic center.

Patient(s): Ninety nine women with ≥2 prior cycles, at a starting dose of ≥300 IU gonadotropins, who yielded fewer than five oocytes or a prior cycle cancellation.

Intervention(s): In the LPG group (n=52), transdermal E2 initiated every other day starting day 10 after the luteinizing hormone (LH) surge; one day 11, patients began daily administration of antagonist for 3 consecutive days, with gonadotropins started on the second day of menstruation. In the LA group (n=47), letrozole 5 mg/day initiated on the second day of spontaneous menstruation for 5 days then gonadotropins added on day 5; for both groups a flexible antagonist protocol was used.

Main Outcome Measure(s): Ongoing pregnancy, number of oocytes retrieved, and cancellation rate.

Result(s): The total dose of gonadotropins administered and E2 levels on day of hCG administration were statistically significantly lower with the LA protocol. The number of oocytes retrieved (6.1±3.0 vs. 7.9±4.8), number of transferred embryos (2.2±1.0 vs. 2.4±1.4), and cancellation rate (55.3% vs. 36.5%) were similar in both groups. Ongoing pregnancy rates per transfer (40% vs. 21.2%) and per initiated cycle (19.1% vs. 13.5%) were similar in the LA and LPG groups, respectively.

Conclusion(s): Aromatase inhibitor regimens can be a feasible alternative to the LPG protocol in recurrent low ovarian response.