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Pathogenesis, clinical manifestations, and diagnosis of ovarian hyperstimulation syndrome

Cristiano E Busso, MD
Sérgio Reis Soares, MD
Antonio Pellicer, MD
Section Editor
Robert L Barbieri, MD
Deputy Editor
Kathryn A Martin, MD


Ovarian hyperstimulation syndrome (OHSS) occurs when the ovaries are hyperstimulated and enlarged due to fertility treatments (or rarely, mutations in the follicle-stimulating hormone [FSH] receptor), resulting in the shift of serum from the intravascular space to the third space, mainly to the abdominal cavity. In its severe form, OHSS is a life-threatening condition because it can cause venous or arterial thromboembolic events, including stroke and loss of perfusion of an extremity.

The pathogenesis, clinical manifestations, and diagnosis of OHSS are reviewed here. The prevention and management of OHSS are discussed separately. (See "Prevention of ovarian hyperstimulation syndrome" and "Management of ovarian hyperstimulation syndrome".)


OHSS is the most serious complication of controlled ovarian hyperstimulation (COH) for assisted reproduction technologies (ART). It is a broad spectrum of signs and symptoms that include abdominal distention and discomfort, enlarged ovaries, ascites, and other complications of enhanced vascular permeability [1,2]. The pathophysiology of OHSS is not fully understood, but increased capillary permeability with the resulting loss of fluid into the third space is its main feature. In the susceptible patient, human chorionic gonadotropin (hCG) administration for final follicular maturation and triggering of ovulation is the pivotal stimulus for OHSS, leading to overexpression of vascular endothelial growth factor (VEGF) in the ovary, release of vasoactive-angiogenic substances, increased vascular permeability, loss of fluid to the third space, and full-blown OHSS.

OHSS is an iatrogenic and potentially life-threatening condition that affects young, healthy patients. In addition, there is an important economic burden associated with OHSS due to absence from work, bed rest, or hospitalization and intensive medical management of severe cases.

There are two clinical forms of OHSS, both hCG related: the early-onset form (occurring in the first eight days after hCG administration) and the late-onset form (occurring nine or more days after hCG administration, related to pregnancy-induced hCG production) [3].

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Literature review current through: Nov 2017. | This topic last updated: Jul 12, 2017.
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