New algorithm for OHSS prevention

Ovarian hyperstimulation syndrome (OHSS) still remains a life-threatening complication of in vitro fertilization treatment (IVF), keeping patients and especially those, who previously experienced OHSS, from attempting infertility treatment and childbearing. The recent implementation of four new modalities: the GnRH antagonist protocol, GnRH agonist (GnRHa) triggering of ovulation, blastocyst transfer and embryo/oocyte vitrification, renders feasible the elimination of OHSS in connection with ovarian hyperstimulation for IVF treatment. The proposed current algorithm is based on the number of follicles developed after ovarian stimulation, setting a cut-off level at the development of 18 or more follicles. Further, fulfilling this criterion, the algorithm is based on four decision-making points: the final day of patient work-up, the day of triggering final oocyte maturation, day-1 post oocyte pick-up (OPU) and day-5 post OPU. If the physician decides to administer hCG for final oocyte maturation regardless the type of analogue used, he has the option on day-1 to either freeze all embryos or to proceed to day-5. On this day, based on the clinical condition of the patient, a decision should be made to either transfer a single blastocyst or to vitrify all blastocysts available. However, this strategy will not guarantee an OHSS free luteal phase especially if a pregnancy occurs. If the physician decides to trigger ovulation with GnRHa, feasible only with the antagonist protocol, embryos can be cultured until day-5. On this day a transfer can be performed with no risk of OHSS and spare blastocysts may be vitrified. Alternatively, on day-1 or day-2 post OPU, all embryos could be frozen. Hopefully, in a near future, GnRHa triggering and vitrification of oocytes will become everyday practice. Only the combined use of a GnRH antagonist protocol with GnRHa triggering and subsequent single blastocyst transfer or embryo/oocyte freezing will completely abolish the risk of OHSS after ovarian hyperstimulation.