Thrombosis following ovarian hyperstimulation syndrome.

The aim of this review is to analyse the pathophysiology and complications of thrombosis in conjuction with ovarian hyperstimulation syndrome (OHSS) following ovulation induction and to suggest practical guidelines usefull for the prevention and treatment. Although the incidence of thrombosis varies from 0.2% among in vitro fertilization (IVF) cycles and up to 10% for severe cases of the syndrome, it represents the most dangerous complication of OHSS. Different changes in haemostatic markers have been found to create a state of hypercoagulability, but no single standard test is available to estimate the state of thrombosis. The role of markers for thrombophilia is controversial. Thromboses are mostly venous (67-75%) involving upper limbs and neck, then arterial (25-33%) which are mainly intracerebral. The predominant sites of venous thromboembolism in the upper part of the body may be explained by higher concentrations of estrogens drained through lymphatic ducts from ascites and by compression of rudimentary branchyal cysts. Once early diagnosis is established, it is crucial to use an anticoagulant treatment with heparin proceeded with thromboprophylaxis. However, identification of patients at risk and preventive measures of OHSS are the best means in reducing the risk of thrombosis after ovarian stimulation.