Ovarian hyperstimulation syndrome prevention strategies: cryopreservation of all embryos

Ovarian hyperstimulation syndrome (OHSS) is an iatrogenic potentially life-threatening condition resulting from excessive ovarian stimulation. The crucial event in the development of OHSS is the administration of human chorionic gonadotropin (hCG). The early onset of OHSS typically presents in the luteal phase as a consequence of ovulatory hCG. The late onset of OHSS presents in early gestation when endogenous hCG further stimulates the ovary. Many strategies have been proposed for OHSS prevention, but they may reduce but not eliminate the risk. This article reviews the evidence related to the elective cryopreservation of all embryos and their subsequent transfer in women at risk of OHSS. More research is needed to determine whether using elective cryopreservation of embryos can reduce the rate of severe OHSS in in vitro insemination (IVF)/intracytoplasmic sperm injection (ICSI). Results from many retrospective studies are encouraging, but prevention in terms of (1) identification of the high-risk population using new biochemical markers of ovarian response such as anti-Müllerian hormone, (2) tailoring ovarian stimulation and using less aggressive protocols (gonadotropin-releasing hormone antagonists or mild IVF), and (3) blastocyst culture to allow clinical monitoring of early-onset OHSS, with eventual blastocyst cryopreservation, might represent a multistep approach worth further investigation.