GnRH antagonist administration for patients at high risk of severe Ovarian Hyperstimulation Syndrome (OHSS) down regulated GnRH agonist

INTERVENTION: GnRH antagonist versus coasting (care as usual) CONDITION: Ovarian Hyperstimulation Syndrome (OHSS) ; Urological and Genital Diseases ; Complications associated with artificial fertilization PRIMARY OUTCOME: Current information as of 24/08/09:; High quality embryos; ; Initial information at time of registration:; OHSS SECONDARY OUTCOME: Current information as of 24/08/09: ; 1. Days of intervention; 2. Number of oocytes; 3. Pregnancy rate; 4. Number of cryopreserved embryos; 5. Incidence of severe OHSS; ; Initial information at time of registration:; Pregnancy rate INCLUSION CRITERIA: Women undergoing in vitro fertilisation (IVF) or IntraCytoplasmic Sperm Injection (ICSI) trial down regulated with GnRH agonist and at risk of severe OHSS