The Risk of OHSS
Dr. Z. Ben-Rafael (Israel) reviewed the risks of OHSS. Severe OHSS complicates only a few percent of IVF cycles. It is characterized by ovarian enlargement, gastrointestinal symptoms, fluid shift to the third space and therefore intravascular volume depletion. Thrombosis and oliguria are serious complications. Once OHSS develops, only supportive therapy can be offered. Studies have shown that high estradiol level and the simultaneous growth of a large number of follicles are associated with OHSS, but they have only a poor predictive value. Oocyte donors with high estradiol level and many follicles seldom develop OHSS. It is now understood that pregnancy, especially multiple gestation, is associated with the more severe form: late-onset OHSS.
Certain measures can be offered before the embryo transfer to reduce the risk of OHSS. The pre-stimulation identification of those at risk is probably the most important step. Once the stimulation is started and signs of OHSS are present, the gonadotropins can be withheld (coasting), the amount of human chorionic gonadotropin (hCG) to induce the final maturation of oocytes can be reduced, the embryos can be electively frozen, and the number of embryos transferred can be limited. Albumin infusion around the time of retrieval offers little benefit, but animal studies have shown that intravenous immunoglobulins reduce the risk, possibly via anticytokine mechanisms. Dr. Ben-Rafael emphasized that women with allergies are at higher risk (they probably have higher baseline cytokine levels and vascular permeability that predisposes them to fluid shifts). All those who prescribe gonadotropins should be aware of this potentially very serious side effect. The best approach is to identify those at risk and select an appropriate protocol for them. One should not be afraid of canceling high-responders or deciding to electively cryopreserve their embryos. Physicians seldom recommend this, however, as they also consider the financial burden the couple is taking on when entering an IVF cycle, given that the overall incidence of really severe OHSS is low.
From Medscape Ob/Gyn & Women's Health