Embryo freezing for preventing ovarian hyperstimulation syndrome: a Cochrane review

This paper is based on a Cochrane review published in The Cochrane Library, issue 3, 2002 (see www.CochraneLibrary.net for information) with permission from The Cochrane Collaboration and Update Software. Cochrane reviews are regularly updated as new evidence emerges and in response to comments and criticisms, and The Cochrane Library should be consulted for the most recent version of the review. BACKGROUND: Ovarian hyperstimulation syndrome (OHSS) is an iatrogenic condition resulting from an excessive ovarian response to superovulation medication. The objective of this review was to evaluate the effectiveness of cryopreservation (embryo freezing) when compared with human i.v. albumin infusion and with fresh embryo transfer for the prevention of OHSS. METHODS: This was based on a Cochrane Review. Randomized controlled trials in which either human i.v. albumin or cryopreservation of all embryos was used as a therapeutic approach to OHSS were included. The participants were women down-regulated by GnRH agonist, undergoing superovulation in IVF/ICSI cycles. The interventions compared were cryopreservation versus i.v. human albumin administration and elective cryopreservation of all embryos versus fresh embryo transfer. The primary outcomes were: incidence of moderate and severe OHSS versus nil/mild OHSS, and clinical pregnancies/woman. Statistical analysis was performed in accordance with the Cochrane Menstrual Disorders and Subfertility Group guidelines. RESULTS: Seventeen studies were identified, two of which met our inclusion criteria. One study was included where cryopreservation was compared with i.v. human albumin administration and another where elective cryopreservation of all embryos was compared with fresh embryo transfer. In both interventions no difference was found in all the outcomes examined between the two groups. CONCLUSIONS: This review has shown that there is insufficient evidence to support routine cryopreservation and insufficient evidence for the relative merits of i.v. albumin versus cryopreservation.