Ovarian hyperstimulation syndrome, or OHSS, is a condition that causes the ovaries to swell. It typically occurs as an adverse effect of fertility medications.

A successful pregnancy may require the support of fertility treatments, which may involve administering hormones. As with most medical interventions, fertility treatments have possible side effects.

OHSS may be mild, moderate, or severe, but most people recover. Although it can sometimes require hospitalization, it rarely results in death.

There is no cure for the condition, but doctors may recommend management strategies, such as IV fluids and blood thinners.

Keep reading to learn more about OHSS, including its symptoms, causes, and risk factors, and how doctors might treat people with this condition.

OHSS occurs when the ovaries swell and leak fluid into the abdomen and potentially other organs. Severe cases can be life threatening.

It is an iatrogenic and serious complication that results from excessive ovarian stimulation. Iatrogenic means that the cause of the disease is medical examinations or treatments.

In the case of OHSS, certain fertility treatments are the cause. For instance, in vitro fertilization (IVF), which stimulates the ovaries to increase the production of eggs, can cause OHSS.

OHSS can occur in up to 30% of all IVF cycles. Estimates suggest that moderate to severe cases of the condition occur in 1–5% of IVF cycles.

In rare cases, the condition can occur with no obvious cause.

Learn more about the IVF process.

OHSS can vary in severity, being mild, moderate, or severe. The most severe cases can become critical.

The severity of the condition will determine the symptoms.


The symptoms of mild OHSS may include:

Moderate OHSS

Moderate OHSS tends to produce the same symptoms as mild OHSS, but an ultrasound may show fluid in the abdomen, which can spread to other organs.

Severe OHSS

In addition to the signs and symptoms of mild and moderate OHSS, a person may experience:

Critical OHSS symptoms

Doctors will define OHSS as critical if these symptoms are present:

The exact cause of this condition is not well-understood.

However, experts believe that an excess of a pregnancy hormone called human chorionic gonadotropin (hCG) triggers the condition. The cells surrounding a growing embryo, which go on to form the placenta, are responsible for producing hCG.

IVF treatment may use gonadotropins to stimulate the ovaries.

An atypical, or excessive, response to this drug can cause the overstimulated ovaries to become enlarged and release chemicals into the blood. These actions may lead to swelling and the leaking of fluid into the abdomen. In severe cases, fluid may leak into the space around the heart or lungs.

Learn more about fertility drugs for females.

Certain factors may increase a person’s risk of developing OHSS. These include:

  • having polycystic ovary syndrome
  • being younger than 30 years
  • having had OHSS previously
  • getting pregnant and developing symptoms in the same IVF cycle, especially if it is a multiple pregnancy

An early diagnosis of OHSS is beneficial in helping a person manage or even prevent their symptoms.

Doctors can use certain tests to determine whether a person has OHSS.

The tests include:

  • a physical exam, to check the person’s weight and waist measurement and look for signs of swelling
  • an ultrasound, to reveal any fluid in the abdomen and the size of the ovaries
  • a chest X-ray, to check whether there is fluid in the chest
  • blood tests, to assess hormone levels that may indicate OHSS

OHSS treatment depends on the severity of a person’s symptoms. The condition typically gets better in time. Although there is no cure, a person can manage their symptoms and prevent complications.


For people with mild OHSS, symptom management may involve:

  • staying physically active to prevent blood clots
  • relieving pain with medications such as acetaminophen
  • avoiding anti-inflammatory drugs such as ibuprofen and naproxen, which can harm the kidneys
  • taking anti-sickness drugs to reduce nausea and vomiting

Moderate OHSS

A person with moderate OHSS can try:

  • using similar approaches to those for managing mild OHSS symptoms
  • receiving an IV drip to replace fluids if severe dehydration occurs or nausea makes it difficult to eat and drink enough
  • wearing support stockings
  • receiving blood-thinning injections to prevent blood clots

Severe OHSS

Additional medical intervention may be necessary to manage a severe case of OHSS. Doctors may recommend:

  • undergoing a paracentesis, in which a doctor inserts a thin needle or tube into the abdomen to remove fluid
  • lowering the dosage of any fertility medications, such as gonadotropins, leuprolide, or cabergoline
  • freezing embryos and delaying their transfer until the symptoms improve
  • taking medications to reduce ovarian activity

If a person develops critical OHSS, they will need to be admitted to the hospital.

The symptoms of OHSS tend to present a few days after ovulation and usually disappear within 2 weeks.

However, in the event of pregnancy, the symptoms may last for 2–3 weeks following a positive test. They often gradually resolve without affecting the rest of the pregnancy.

Becoming pregnant again

Doctors recommend wearing support stockings and receiving blood-thinning injections until week 12 of pregnancy. This is to reduce the risk of developing blood clots in the legs or lungs.

Having OHSS may increase the risk of preeclampsia or premature delivery, but no known risks exist in relation to infant development. Preeclampsia refers to an increase in blood pressure and the presence of protein in the urine during pregnancy.

OHSS commonly occurs as a result of receiving fertility treatments.

These treatments can cause the ovaries to swell and leak fluid into the abdomen and other organs.

Most people who develop OHSS have only mild or moderate symptoms. Although there is no cure, doctors can recommend a range of symptom management methods, such as pain relievers, anti-sickness medications, IV fluids, and paracentesis.