Ovarian hyperstimulation syndrome

The Royal College of Obstetricians and Gynaecologists defines ovarian hyperstimulation syndrome (OHSS) as a “systemic disease resulting from vasoactive products released by hyperstimulated ovaries”. It is usually the result of gonadotrophin stimulation for in vitro fertilisation (IVF), with moderate and severe cases affecting about 3–8% of cycles. At the heart of OHSS is an increase in vascular permeability causing the movement of fluid out of the intravascular space, with resultant accumulation of fluid in the third space and intravascular depletion. The diagnosis is made according to recognised signs, symptoms and investigations on a background of ovarian stimulation. Prevention is better than cure in this iatrogenic disorder, but the aim of management is effective monitoring to confirm safe spontaneous improvement or alert the requirement for intervention in the event of deterioration; the crux of which concerns careful fluid management. This article reviews the pathogenesis, diagnosis, classification and management of OHSS.