What is ovarian hyperstimulation syndrome (OHSS)?

Ovarian hyperstimulation syndrome (OHSS) occurs when a woman’s ovaries swell and leak fluid into the body. This condition is a complication that can occur in women who receive fertility treatments that stimulate the ovaries to produce more eggs than usual, but there are rare cases of OHSS occurring spontaneously.

In the past, OHSS was a relatively common complication of in vitro fertilization (IVF). New protocols and strategies have made this condition rare, except for mild cases.

OHSS is more common in women receiving fertility treatments who have polycystic ovarian syndrome (PCOS). PCOS is a reproductive disorder involving a hormonal imbalance.

Most cases of OHSS are mild and cause temporary discomfort. Severe cases of the condition are rare but can be life-threatening.

How common is ovarian hyperstimulation syndrome (OHSS)?

OHSS used to occur in about 10% of women who receive in vitro fertilization treatments, but today the number is less than 5%. Severe cases of the condition happen in less than 1% of women receiving hormonal fertility treatments.

What causes ovarian hyperstimulation syndrome (OHSS)?

In most cases, OHSS develops because of high levels of the pregnancy hormone hCG following fertility treatments that stimulate the production of many eggs at one time, as is done with many IVF protocols. In very rare cases, patients have genetic mutations in certain hormone receptors that predispose them to developing OHSS even without hormonal treatments.

In women with OHSS, drugs used in fertility treatments cause the blood vessels surrounding the ovaries to leak fluid. This fluid causes the ovaries to swell. Sometimes this fluid moves into the belly and other areas, causing:

• Swelling.
• Pain.
• Nausea.
• Vomiting.
• Increased thirst.

In severe forms, the excess fluid can result in difficulty breathing and decreased urination.

What are the symptoms of ovarian hyperstimulation syndrome (OHSS)?

The signs and symptoms of OHSS vary depending on the severity of the condition. Symptoms of mild to moderate OHSS include:

• Abdominal pain.
• Bloating.
• Sleight weight gain.
• Nausea.

In more severe cases of OHSS, symptoms may include:

• Excessive weight gain.
• Severe nausea and vomiting.
• Severe abdominal swelling.
• Difficulty breathing.
• Blood clots.
• Decreased urination.
• Kidney failure.
• Severe abdominal pain.

How is ovarian hyperstimulation syndrome (OHSS) diagnosed?

Doctors diagnose OHSS with several tests. These tests can include:

• Physical exam: Checks your weight and measures the size of your waist to look for signs of swelling.
• Ultrasound: Looks for free fluid in the abdomen and the size of the ovaries.
• Chest X-ray: Looks for fluid in the chest.
• Blood test: Measures hormone levels for signs of OHSS.

How is ovarian hyperstimulation syndrome (OHSS) managed or treated?

The treatment for OHSS varies depending on how severe the condition is. Treatment aims to manage symptoms and avoid complications.

For mild to moderate cases of OHSS, treatment usually involves:

• Avoiding vigorous physical activity.
• Increasing oral intake of fluids.
• Using acetaminophen to relieve symptoms.
• Weighing yourself daily.
• Monitoring yourself for any severe symptoms.

Severe cases of OHSS often require hospitalization. Treatment of severe OHSS may include:

• Adjusting your fertility medication dose.
• Receiving intravenous (directly into the vein) fluids.
• Freezing your embryos and delaying their embryo transfer until the ovaries return to normal.
• Undergoing paracentesis (a procedure to remove fluid from the belly).
• Taking medicines to ease symptoms or reduce activity in the ovaries.

What complications are associated with ovarian hyperstimulation syndrome (OHSS)?

Women with OHSS are at risk for developing a thrombosis (blood clot) in the lungs or legs. Medicines can help decrease your risk for this complication. Tell your healthcare provider if you experience a painful, swollen leg or chest pain.

In rare cases, an ovarian cyst associated with OHSS can burst. Women with this complication may need surgery to stop the dangerous bleeding that can occur as a result.

What are the risk factors for ovarian hyperstimulation syndrome (OHSS)?

Women at a higher risk for OHSS include those who:

• Have PCOS.
• Have previously had OHSS.
• Have a large number of follicles or high level of estrogen during IVF stimulation.
• Received high doses of hCG during an IVF cycle.
• Have undergone a “fresh” rather than “frozen” embryo transfer.

In addition, while there is not clear evidence, there may be a higher risk for OHSS in those who:

• Are younger than 30 years old.
• Weigh less than normal.

Can ovarian hyperstimulation syndrome (OHSS) be prevented?

Some cases of OHSS cannot be prevented. If you are having fertility treatments, your doctor may monitor your ovaries regularly with blood tests and ultrasounds to reduce the risk of OHSS.

What is the prognosis (outlook) for people with ovarian hyperstimulation syndrome (OHSS)?

OHSS is temporary. In most women the condition goes away within two weeks. Even severe cases have a positive outlook when treated promptly. If the fertility treatment is successful, having OHSS does not pose any risk to your baby.

When should I call the doctor?

Contact your doctor if you are receiving fertility treatments and experience the symptoms of OHSS.

What questions should I ask my doctor?

If you have OHSS, you may want to ask your doctor:

• How severe is my condition?
• What are my treatment options?
• What signs of complications should I look out for?
• Will OHSS harm my chances of becoming pregnant or affect the baby?

When can I go back to my regular activities?

Healing times for OHSS vary depending on the severity of the condition. Your doctor will tell you when you can return to your usual activities.