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 flar e (short) or down-regulation (long) regimen as part of IVF or GIFT treatmen t 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, incl uding E-2 level, number of oocytes retrieved, and clinical pregnancy rate. Result(s): At site I, there were 146 clinical pregnancies in 980 flare cycl es, for a pregnancy rate of 14.9%, compared with 148 clinical pregnancies i n 650 down-regulation cycles, for a pregnancy rate of 22.8%. This differenc e persisted after adjustment for age, primary infertility diagnosis, GIFT o r IVF therapy, and year of treatment, and appeared to be mediated largely b y the number of oocytes retrieved (mean, 9.8 for down regulation and 8.7 fo r 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 di fference was not explained by patient selection factors. (Fertil Steril(R) 1999;72:83-9. (C)1999 by American Society for Reproductive Medicine.).