Ovarian hyperstimulaiton syndrome (OHSS) is a relatively uncommon complication of fertility treatment. The true incidence is unknown. It results from an excessive ovarian response to stimulation by follicle stimulating hormone (FSH), with subsequent responses to human chorionic gonadotrophin (hCG) and/or luteinising hormone (LH).
Pathophysiology
The action of hCG on hyperstimulated ovaries causes a release of proinflammatory cytokines. Vascular endothelial growth factor (VEGF) increases vascular permeability and leads to loss of fluid into the “third space”; this commonly manifests as ascites. The reduction in intravascular fluid volume produces a hypovolaemia with haemoconcentration and paradoxical hypoösmolality.
The life threatening complications such as acute respiratory distress syndrome (ARDS), renal failure, and thrombosis result from the disturbed physiology: third spacing, hypovolaemia, and proimflammatory/prothrombotic state (or perhaps hyperviscosity) respectively. Severe ovarian haemorrhage may also occur as a result of ovarian rupture.
Further reading
- Marthur R, Drakeley A, Raine-Fenning N, Evbuomwan I, Hamoda H. The Management of Ovarian Hyperstimulation Syndrome. Green Top Guideline No. 5. London: Royal College of Obstetricians and Gynaecologists; 2016.