What is Ovarian Hyperstimulation Syndrome?

Jan 11, 2023


Alto Pharmacy

Some injectable fertility medications increase your levels of the pregnancy hormone, human chorionic gonadotropin (hCG). Ovarian hyperstimulation syndrome (OHSS) develops when the blood vessels in your ovaries have an abnormal response to the presence of hCG and leak fluid. The condition is characterized by pain and swelling in the ovaries and sometimes the abdomen.

Once considered a more common complication of IVF, OHSS cases have declined over the years. It currently affects less than 5% of all those who undergo the fertility treatment. Less than 1% of all individuals pursuing hormonal fertility treatments experience severe OHSS.

Let’s take a look at what causes this relatively rare IVF complication and how to prevent it during your cycle.

Causes and risk factors

OHSS most often occurs as the result of injectable fertility medications used to stimulate egg growth and trigger egg release during IVF or egg freezing. Oral fertility medications are a less common cause of OHSS. It may also develop spontaneously in rare cases.

The following factors may increase your risk for OHSS, but they aren’t necessary for it to develop.

If you experience OHSS during one round of fertility treatment, you may be more likely to experience it again.

Symptoms of OHSS

When OHSS develops during IVF, symptoms typically appear within a week of the first injection of stimulation medication. However, it may take two weeks or more for symptoms to develop.

Symptoms vary by the severity of the condition. Mild to moderate cases often include mild abdominal swelling, bloating, and nausea, as well as minor weight gain.

More severe cases include severe abdominal pain and swelling, bloating, and nausea, and much more noticeable weight gain. Difficulty breathing, blood clots, decreased urination, and impaired kidney function can also occur in these cases.

While the majority of OHSS cases are mild and don’t require treatment, tell your healthcare provider about any potential symptoms. They will require monitoring regardless of their intensity.

Without prompt, effective treatment, severe cases of OHSS can lead to serious complications, including a blood clot in the lungs or legs, or a ruptured ovarian cyst. Seek immediate care from your provider if at any point during your fertility treatment you have trouble breathing or feel pain or swelling in your legs or chest.

Treatment for OHSS

Doctors may recommend gonadotropin-releasing hormone (Gn-RH) antagonists or letrozole to treat moderate to severe symptoms of OHSS. These medications suppress ovarian activity.

In some cases, a doctor may recommend canceling treatment and starting a new cycle in the future after OHSS symptoms have resolved. Although this can be devastating, remember that many individuals and couples have eventual success with IVF after one or more canceled or unsuccessful cycles.

It may be an option to freeze embryos from IVF and finish the implantation at a later date after your body has recovered from OHSS.


Fortunately, there are steps you can take to lower the risk of OHSS during IVF. If you have any known risk factors, or if you experienced OHSS during a previous cycle, your provider may recommend one or more of the following adjustments to your treatment plan.

Adding medications

A medication called cabergoline is primarily used to prevent cases of OHSS during IVF. GnRH antagonists and letrozole are sometimes also used as preventative treatment.

Metformin — an oral diabetes medication that is sometimes used off-label to treat PCOS — can also be used to reduce the risk of OHSS in women with PCOS.

Adjusting the medication schedule

If you have high levels of estrogen or many developed follicles during IVF, your doctor may adjust the timing or duration of your medication schedule. A common practice is to stop the use of stimulation medications for several days before the trigger shot(s) to prevent further stimulation of a high follicle count.

Lowering the dosage

Injecting the lowest effective dose of a fertility medication can also help prevent OHSS.

Avoiding hCG trigger shot

Your doctor may also recommend using an alternative medication such as leuprolide in place of an hCG trigger shot to prevent OHSS.

Choose a flexible and reliable pharmacy partner

Fertility treatment can be challenging, but we’ll be with you every step of the way. To ensure that your treatment plan is followed correctly, we offer free same-day delivery of your medications and fertility resources like personalized injection guide videos and one-on-one consultations with fertility-trained pharmacists.

Interested in learning more about how Alto can support your fertility treatment? Request a price quote online or reach out through secure in-app messaging or by phone at 1-800-874-5881.

This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or another qualified health provider with any questions you may have regarding a medical condition.