Understanding Ovarian Hyperstimulation Syndrome

Ovarian hyperstimulation syndrome (OHSS) is a possible complication of infertility treatments, whereby the ovaries become enlarged due to cysts and fluid collects.

This complication of assisted reproduction technology and infertility treatments may appear several days after gonadotropin therapy (the injectable hormones used to stimulate ovulation), after an egg is retrieved or ovulation has been assisted.

Ovarian hyperstimulation syndrome can cause problems in multiple organs and if left unchecked, can result in death. Those with polycystic ovarian syndrome (PCOS) are particularly at risk of OHSS because they may already have cystic and slightly enlarged ovaries and are prone to over-responding to the synthetic hormones used.

Your doctor will take this into consideration and use a lower dose of hormones while monitoring you accordingly. The mild form of OHSS is much more common, up to 23 per cent of cases, with moderate and severe OHSS making up about 14 per cent collectively.

There are several classifications and grades of OHSS:

Mild OHSS – grade 1 (abdominal distention and discomfort) or grade 2 (grade 1 plus nausea, vomiting, maybe diarrhoea, ovarian enlargement of 5-12cm)
Moderate OHSS – grade 3 (mild OHSS plus fluid collection under ultrasound)
Severe OHSS – grade 4 (moderate OHSS plus fluid collection and possibly breathing difficulties) or grade 5 (all of the above, plus change in blood volume, increased blood thickness, diminished kidney function)

Symptoms of ovarian hyperstimulation syndrome

Symptoms start 3-7 days after administration of the gonadotropin, hCG, with severe OHSS 12-17 days after hCG administration.

Symptoms occurring >10 days after hCG are thought to be due to the production of hCG from pregnancy. Thus, OHSS cases followed by pregnancy can be serious and take a long time to resolve.

Symptoms include:

Shortness of breath
Small amounts of urine being passed
Lethargy
Quick weight gain
Abdominal discomfort or pain caused by fluid and follicle pressure
Nausea
Vomiting
Pain from follicle/cyst rupture
Pain from inflammation
Pain from ovarian torsion (twisted ovary)
Low blood pressure
Swelling
Blood clotting issues (embolism, deep vein thrombosis)
Kidney dysfunction or failure

Why does ovarian hyperstimulation syndrome develop?

We’re not really sure why this syndrome develops, but we know that one of the main contributors is changes in the way our blood vessels work.

Blood vessels in the ovaries and their surrounding tissues become more permeable, which means fluid leaks out and accumulates where it shouldn’t. OHSS occurrence is mainly due to the administration of human chorionic gonadotropin (hCG) and it rarely happens without this.

Risk factors for ovarian hyperstimulation syndrome

Age 35 or less
Low body mass index (BMI)
Gonadotropin treatments
High oestradiol concentrations
Large numbers of follicles
History of polycystic ovarian syndrome (PCOS)
hCG administration
Increased hCG levels due to pregnancy
If pre-hCG oestradiol is greater than 6,000mcg and/or if more than 30 follicles are present, rate of severe OHSS hits 80 per cent
More likely if ovary is overstimulated
Incidence rises when GnRH agonists and gonadotropins are used together to induce ovulation
Only occurs to fertile-age women

Outcomes of ovarian hyperstimulation syndrome

While it is not unheard of to become quite ill or even to die from OHSS, it is certainly not the norm. Mild or moderate cases of OHSS have excellent outcomes with proper treatment.

The cause of death is largely due to electrolyte imbalance and decreased blood volume, bleeding and excess coagulation. OHSS is estimated to cause death in one woman per 400,000 – 500,000 stimulated cycles.

How to keep yourself out of the danger zone

Record your weight daily
Avoid exercise and sex
Maintain adequate hydration after in vitro fertilisation (IVF)
Measure abdominal girth
Keep note of how many times you urinate, reporting anything less than 1L in a 24-hour period
Report progressive bloating, abdominal discomfort, changes in urinary output, cramping, dizziness, shortness of breath, weight gain of more than 5lb/2kg per week

What else could it be?

Appendicitis
Pelvic inflammatory disease
Abscess
Ovarian cysts
Ovarian torsion
Pericardial effusion
Sepsis
Pulmonary embolism
Pleural effusion

Treatment of ovarian hyperstimulation syndrome

OHSS is a self-limiting condition, which means it’ll sort itself out by itself, so long as it doesn’t become dangerous, however, diagnosis and monitoring by your doctor is essential to ensure the condition does not become dangerous.

Medical interventions are usually enough to get you out of the danger zone, with only severe symptoms requiring hefty medical care. Surgery is not the first port of call, since it can exacerbate the problems.

Treatments according to severity include:

Mild – observation is the main treatment here. Your doctor will usually have you stay at home but attend for regular examination of your abdominal girth, weight gain, fluid retention and discomfort
Moderate – care consists of observation, bed rest, staying hydrated and frequent blood tests to check on markers of severity. This may mean a stay in hospital.
Severe – this is rare but can be lethal so you will definitely be admitted to hospital where you will be closely monitored. Intravenous saline and other solutions may be used to correct your fluid balance. Other treatments include heparin injection to prevent thrombosis and removal of fluid or gas from the abdomen with a needle. Rarely, transfer to intensive care may be necessary.

For all grades, staying hydrated is important, as is not moving around too much. Your doctor must be very careful not to push too hard on your abdomen, as this can burst cysts and cause further problems.

For this reason, avoid sex too. If you have twisted or bleeding ovaries, surgical intervention may be necessary, with fluid management strategies employed.

If you are pregnant, symptoms may worsen, so follow your doctor’s instructions and be diligent in reporting your symptoms to them. You should be monitored for at least two weeks, unless your symptoms worsen or until you get your period. Complete resolution takes about two weeks.