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Comparison of GnRH agonists and antagonists in assisted reproduction cycles of patients at high risk of ovarian hyperstimulation syndrome.

Ragni G, Vegetti W, Riccaboni A, Engl B, Brigante C, Crosignani PG

Infertility Unit, Department of Obstetrics-Gynaecology, University of Milan, Italy. g.ragni@icp.mi.it

BACKGROUND: During IVF or ICSI cycles, ovarian hyperstimulation syndrome (OHSS) is a major problem. The aim of this prospective, multicentre, comparative study (using historical controls) was to assess the efficacy of a GnRH antagonist protocol in preventing OHSS in selected patients who had experienced OHSS or had been at risk of OHSS in their previous IVF/ICSI attempt. METHODS AND RESULTS: Patients underwent a new cycle where the same gonadotrophin protocol was used [same dose of recombinant FSH (rFSH)] but a different protocol was used for pituitary desensitization: cetrorelix 0.25 mg multiple-dose antagonist instead of GnRH agonist long protocol. Cetrorelix 0.25 mg was administered daily, starting when the leading follicle reached a diameter of 14 mm. In other words, rFSH was administered in the new cycle according to the dosage and the step-up or step-down modalities used during the previous cycle, independently of ultrasound findings and serum estradiol (E(2)) levels. Eighty-seven patients entered the study. Out of the 87 cycles involving GnRH agonists, 49 (56.3%) were cancelled and out of the 87 involving GnRH antagonists 28 (32.2%) were cancelled [McNemar's test; 95% confidence interval (CI) -35.8% to -11.2%; P < 0.001]. After GnRH agonist cycles, we recorded 24 cases of OHSS (18 moderate and six severe; 27.6%), whereas after the GnRH antagonist cycles there were 10 cases of OHSS (nine moderate and one severe; 11.5%) (95% CI-26.4% to -5.7%; P = 0.006). There was a statistically significant reduction in the total number of follicles with a diameter >10 mm (Wilcoxon's test; Z = 6.1; P < 0.001) and of E(2) levels on the day of HCG administration (2538 versus 4322.4 pg/ml; P < 0.001) in the GnRH antagonist cycles versus GnRH agonist cycles. Twenty-nine patients had an embryo transfer in the first cycle (76.3% of oocyte retrievals) and 57 in the cycle using GnRH antagonist (96.6%). This 20.3% difference was also significant (Z-test; 95% CI 6.8-36.0%; P = 0.003). After the antagonist cycles, 18 pregnancies (20.7 per initiated cycle; 31.6% per embryo transfer) were obtained. CONCLUSIONS: Although this study presents some limitations owing to the use of historical controls, our data show a favourable effect of GnRH antagonists in reducing the incidence of OHSS and the number of assisted fertilization cycles cancelled because of the risk of OHSS in high responder patients. As a consequence, GnRH antagonist plus gonadotrophin administration could also increase the percentage of oocyte retrievals and embryo transfers in this high risk group of patients.

Published 11 August 2005 in Hum Reprod, 20(9): 2421-5.
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