High pregnancy rates and successful prevention of severe ovarian hyperstimulation syndrome by 'prolonged coasting' of very hyperstimulated patients: a multicentre study.

In a multicentre trial, 65 in-vitro fertilization (IVF)-embryo transfer cycles were severely hyperstimulated. Instead of cancelling the cycle, gonadotrophins were withheld for a 'coasting period' until serum oestradiol concentrations had dropped below 10,000 pmol/l (mean 4.3 days), and then human chorionic gonadotrophin was administered. Four cycles were cancelled and there were 61 oocyte aspirations. A total of 103 fresh embryos was transferred to 53 patients, resulting in a pregnancy rate of 42% per started cycle (51% per embryo transfer), with an implantation rate of 31%. Only one patient developed severe ovarian hyperstimulation syndrome (OHSS). Four patients developed moderate OHSS. In all, two patients were hospitalized for OHSS. In order to optimize the coasting procedure, it seems important that each IVF centre identifies its appropriate cut-off limits for serum oestradiol concentrations and follicle size for initiating and ending of the coasting period. Correctly handled, it seems to be a major advance in the search for improved stimulation policies for high-responders.