Gonadotropin-releasing hormone agonist use in assisted reproduction cycles: the influence of long and short regimens on pregnancy rates

Objective: To compare the efficacy of GnRH agonists used in either the flare (short) or down-regulation (long) regimen as part of IVF or GIFT treatment cycles. Design: Observational study. Setting: Three IVF clinics. Patient(s): One thousand two hundred forty-four couples accepted for IVF or GIFT treatment at participating clinics. Intervention(s): In vitro fertilization or GIFT protocols standard to each clinic were recorded. Main Outcome Measure(s): Treatment cycle characteristics and outcomes, including E 2 level, number of oocytes retrieved, and clinical pregnancy rate. Result(s): At site 1, there were 146 clinical pregnancies in 980 flare cycles, for a pregnancy rate of 14.9%, compared with 148 clinical pregnancies in 650 down-regulation cycles, for a pregnancy rate of 22.8%. This difference persisted after adjustment for age, primary infertility diagnosis, GIFT or IVF therapy, and year of treatment, and appeared to be mediated largely by the number of oocytes retrieved (mean, 9.8 for down-regulation and 8.7 for flare in the first cycle). Despite having fewer oocytes retrieved, women who received flare regimens had higher E 2 levels before hCG administration. Conclusion(s): Women who received GnRH agonists in a flare regimen had 11% fewer oocytes retrieved and a 35% reduction in the clinical pregnancy rate compared with those who received them in a down-regulation regimen; this difference was not explained by patient selection factors.