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Ovarian hyperstimulation syndrome (OHSS) represents an exaggerated response to controlled ovarian stimulation (COS) that in some cases could be life-threatening. Assuming that complete prevention of OHSS is not possible, several strategies could be carried out to reduce the risk and early identification of risk factors represents the first step of a multi-stage process. Some well-established risk factors that could rise the risk of OHSS include young age, polycystic ovary syndrome, prior hyper-response/OHSS. In recent years research has focus on identifying biomarkers/hormonal markers that could represent potential predictors of OHSS (anti-Mullerian hormone and antral follicle count). The possible prevention strategies available for the clinician could be divided into primary and secondary. Primary prevention includes personalized stimulation protocols in order to suit patients' characteristics (individually tailored COS, use of GnRH antagonist stimulation protocols, in vitro maturation). Secondary prevention includes all strategies directed to counteract an excessive ovarian response (cycle cancellation, coasting, trigger ovulation by low doses of hCG or by alternative agents, cryopreservation of oocytes/embryos, adequate luteal phase support). So far, the combined use of a GnRH antagonist protocol with GnRH agonist triggering and oocyte and embryo freezing could not be recommended as a standard preventive measure, but it surely represents a promising one.

The aim of this prospective observational study is to determine the different outcomes of IVF/ICSI treatments after using antagonists or agonists of gonadotrophin-releasing hormone (GnRH) for controlled ovarian hyperstimulation (COH) in normal responder patients. Two hundred forty-seven patients undergoing IVF treatment at the Centre of Reproductive Medicine, Rome (CERMER), from January 2005 to December 2008, were included in the study. Patients were stimulated either with a standard long protocol with GnRH agonists (n = 156) or with GnRH antagonists (n = 91). The use of GnRH antagonists resulted in a significant reduction in the duration of the stimulation (Agonist Group 14.10 ± 2.25 vs Antagonist Group 11.34 ± 2.11; p < 0.001) and in the amount of gonadotrophin (IU of r-FSH) needed (Agonist Group 1878 ± 1109 vs Antagonist Group 1331 ± 1049; p = 0.0014). Moreover a lower number of cycles were cancelled with the antagonist protocol (4.39 vs 6.41%). The GnRH antagonist protocol, when compared to the GnRH agonist one, is associated with a similar clinical pregnancy rate, similar implantation rate, significantly lower gonadotrophin requirement and shorter duration of stimulation. For this reason, GnRH antagonists might be a good treatment even for normal responder patients undergoing IVF.

In modern society, obesity has become a major health problem and has been associated with impaired fertility. The aim of this study is to assess the role of obesity in women undergoing controlled ovarian hyperstimulation (COH) stimulated either with GnRH agonists or with GnRH antagonists. Records of 463 women undergoing in vitro fertilization (IVF) treatment were reviewed. The influence of body mass index (BMI) on treatment outcome was examined, after accounting for differences in stimulation protocols. In the agonist group (286 patients), the total amount of gonadotropins used was significantly higher in patients with a BMI ≥ 25 kg/m², when compared to those with a normal BMI. The same result was found in the antagonist group (177 patients). No significant differences were found in length of stimulation, number of oocytes retrieved or number of embryos transferred. In both the antagonist and the agonist group, the number of clinical pregnancies was found to be higher in patients with normal BMI, suggesting that obesity could impair the ovarian response to exogenous gonadotropins. Considering the results obtained and the many theoretical advantages of GnRH antagonists, ovarian stimulation with GnRH antagonists is an efficient treatment for both women with normal and high BMI.