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New algorithm for OHSS prevention

Evangelos G Papanikolaou17*, Peter Humaidan2, Nikos Polyzos3, Sofia Kalantaridou4, Sahar Kol5, Claudio Benadiva6, Herman Tournaye3 and Basil Tarlatzis7

Author Affiliations

1 Human Reproduction & Genetics Foundation, Adrianoupoleos 6, 55133 Kalamaria, Thessaloniki, Greece

2 The Fertility Clinic Odense University Hospital (OUH) Boulevard 29, entrance 55 5000 Odense C, Denmark

3 Centrum voor Reproductieve Geneeskunde, UZ Brussel, Flemish Free university of Brussels, Belgium

4 Department of Obstetrics and Gynecology, University of Ioannina, Greece

5 Department of Obstetrics and Gynecology, IVF Unit, Rambam Medical Center, Haifa, Israel

6 Center for Advanced Reproductive Services, University of Connecticut School of Medicine, Department of Obstetrics and Gynecology, Farmington, Connecticut, USA

7 Assisted Reproduction Unit, 1st Department of Obstetrics and Gynecology, Aristotle University of Thessaloniki, Greece

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Reproductive Biology and Endocrinology 2011, 9:147  doi:10.1186/1477-7827-9-147

Published: 3 November 2011


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.