Ovarian hyperstimulation syndrome

Ovarian hyperstimulation syndrome (OHSS) is a complication from some forms of fertility medication. Most cases are mild, but a small proportion is severe.

Symptoms

Patients experience weight gain, edema, and abdominal distention and pain. In more severe cases difficulty in breathing is encountered.

Classification

In mild forms of OHSS the ovaries are enlarged, in moderate forms there is additional accumulation of ascites with mild abdominal distension, while in severe forms of OHSS there may be hemoconcentration, thrombosis, abdominal pain and distension, oliguria (decreased urine production), pleural effusion, and respiratory distress. Early OHSS develops before pregnancy testing, and late OHSS is seen in early pregnancy.

Pathophysiology

OHSS is characterized by the presence of multiple luteinized cysts within the ovaries leading to ovarian enlargement and secondary complications.

As the ovary undergoes a process of extensive luteinization, large amounts of estrogens, progesterone, and local cytokines are released. It is held that vascular endothelial growth factor (VEGF) is a key substance that induces OHSS by making local capillaries "leaky" leading to a shift of fluids from the intravascular system to the adbominal and pleural cavity. Thus, while the patient accumulates fluid in the third space, primarily in the form of ascites, she actually becomes hypovolemic and is at risk for respiratory, circulatory, and renal problems. Patients who are pregnant sustain the ovarian luteinization process by the production of hCG.

Epidemiology

Sporadic OHSS is very rare, and may have a genetic component. Clomifene citrate therapy can occasionally lead to OHSS, but the vast majority of cases develop after use of gonadotropin therapy (with administration of FSH), such as Pergonal, and administration of hCG to trigger ovulation, often in conjunction with IVF. The frequency varies and depends on patient factors, management, and methods of surveillance. About 5% of treated patients may encounter moderate to severe OHSS.

Mortality is low, but several fatal cases have been reported.

Treatment

Physicians can reduce the risk of OHSS by monitoring of FSH therapy to use this medication judiciously, and by withholding hCG medication. Once OHSS develops, reduction in physical activity, monitoring fluid and electrolyte balance, and aspiration of accumulated fluid from the abdominal/pleural cavity may be necessary. Over time the condition will naturally reverse to normal.

References

Delvigne A, Rozenberg S. Epidemiology and prevention of ovarian hyperstimulation syndrome (OHSS): a review. Hum Reprod Update 2002;8:559-77. PDF. PMID 12498425.
Delvigne A, Rozenberg S. Review of clinical course and treatment of ovarian hyperstimulation syndrome (OHSS). Hum Reprod Update 2003;9:77-96. PDF. PMID 12638783.