Ovarian Hyperstimulation Syndrome: Causes, Types, Symptoms. Prevention & Treatment

28 June 2021

Ovarian hyperstimulation syndrome or OHSS is a condition where there is a hyper response in the ovary, and more eggs are produced inside the ovary.

Normally it is an iatrogenic problem (it happens because of the treatment rather than the disease ). Ovarian response and its effect on the body varies between different patients.

Ovarian hyperstimulation syndrome can happen in any type of fertility treatment from a simple oral drug to injections used for IVF or other treatments.

In very rare conditions such as gestational trophoblastic disease, pituitary tumours OHSS develop without any treatment, but this syndrome mainly arises because of the medical treatment.

Causes

OHSS is caused by ovarian stimulation by various drugs. These drugs are used to create more follicles for treatments such as ovulation induction, IUI, or IVF.

Women having PCOS are at a much greater risk of OHSS than other patients.

When there is a hyper response, it can cause various symptoms. It was a relatively difficult problem to treat in the past, but now, with the various treatment modalities available with the IVF treatment and embryo freezing its impact can be reduced significantly. Embryo freezing is done by a very safe and effective vitrification method. with this method we get equivalent results to fresh transfer. OHSS is a self limiting condition.

Freezing gives us time for ovaries to reduce in size, once everything is normal we can plan embryo transfer.

The syndrome can be severe in women under 35 years of age because they have more follicles in their ovary, so they are more prone to develop follicles.

Underweight women also have more symptoms of OHSS.

Types

OHSS can be of two types: Primary and Secondary.

Primary OHSS means OHSS that happens by fertility medication used to stimulate egg growth. The medications create more eggs causing the ovaries to enlarge and cause symptoms of OHSS

However, this ovarian enlargement is temporary. If we stop fertility medicines there will be no further stimulation and OHSS will likely regress on its own. However till the ovarian size and other parameters become normal there may be symptoms and complications.

Secondary OHSS occurs during pregnancy. The pregnancy hormone that is the hCG hormone will continuously stimulate the ovaries. Secondary OHSS can be more severe than primary OHSS

Symptoms

The symptoms are mainly due to enlarged ovaries. It causes the distention of the abdomen, pain inside the abdomen.

There will be hormonal changes because of developing eggs. It will cause the loss of fluid into the extravascular space ( outside of the blood vessels) so the blood is thickened. The fluid in the extravascular space is collected inside the abdomen and around other organs. This leads to the distention of the abdomen. The thickened blood is prone to clotting, there are chances of blood clot formation in different body organs. The effects of this clots will depend on its location and size.

Nausea and vomiting can also be the symptoms of OHSS.

Most cases of OHSS are mild, but rarely the condition is severe and can lead to serious illness or death.

Prevention

We at Bavishi Fertility Institute have devised our own criteria to have OHSS free IVF treatment. For the last 7 years, we haven't seen any patient with severe OHSS. As discussed, primary OHSS is not severe. If there is no pregnancy there will be no secondary OHSS.

When in doubt, we freeze the embryos. The ovaries will regress in size naturally. Once the ovaries have come to normal size satisfactorily only then we will transfer the frozen embryos and achieve the pregnancy.

Using this method does not reduce the success rate.Sometimes it can also give us a higher success rate as we transfer the embryos when there are no hormonal disturbances.

In IVF, we target 8-15 numbers of eggs. Sometimes we get more eggs than intended. In these patients whether to do a fresh transfer or frozen transfer is a question. We have devised our own criteria whether to do fresh transfer or not in case of the marginally increased number of eggs.

The criteria are based on the patient's symptoms, the ovarian size, blood estrogen level, blood hematocrit level to check whether the blood has thickened or not. If all these parameters are normal and the patient is asymptomatic, then we can go for fresh transfer.

By following this criterias, we have not seen severe OHSS for the last 7 years.

For patients who have suffered OHSS, there are various stimulation methods such as minimum stimulation IVF, modified natural IVF, natural IVF where we use a very small amount of drug, which can reduce the OHSS chances to almost zero.

To further help, we can freeze all embryos in patients who have had a history of OHSS, so the chances of ovarian hyperstimulation will be close to zero.

Treatment

Mild cases usually do not require any treatment, and symptoms resolve on their own. As the number of days will pass from the ovum pickup or ovulation, the ovaries will gradually reduce in size, and hormone changes will gradually reverse. The injection that is commonly used from ovulation has a half-life of up to 72 hours, so for 3 days, the symptoms may worsen, but after that, the symptoms will gradually resolve.

During this time, we must avoid any complications that can happen from OHSS. You need to keep proper hydration and check urine output. If there is a reduction in urine output, then, in that case, medical help is required.

Take care to avoid direct trauma to the abdomen because the ovaries are enlarged, and they can get injured.

Avoid vigorous movement and intercourse. as this may cause the twisting of the ovaries, which may require various forms of medical and surgical interventions.

It is advised to keep track of fever. If there is any fever, please report to a doctor. In severe cases, hospitalization is required. Even after hospitalization, the treatment is mainly supportive. This includes intravenous fluids and supportive medicines. There may be a need to aspirate fluids from the abdomen.

We need to avoid clot formation. For this we suggest a light degree of movement whenever possible. Move your foot up and down at the ankle to avoid blood clot formation inside the leg. LMWH-heparin injections may be suggested for blood thinning. Other treatment depends on patient's condition.

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