Ovarian hyperstimulation syndrome

Overstimulated Ovaries

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, 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.

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:

  1. Mild OHSS – grade 1 (abdominal distention and discomfort) or grade 2 (grade 1 plus nausea, vomiting, maybe diarrhoea, ovarian enlargement of 5-12cm)
  2. Moderate OHSS – grade 3 (mild OHSS plus fluid collection under ultrasound)
  3. 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 hCG, with severe OHSS 12-17 days after hCG administration
  • Mild or moderate (early) usually due to administration of hCG, while late is usually due to hCG increases due to pregnancy
  • 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 one of the main contributors is increases in the way our blood vessels work – it seems that the ovaries and their surrounding tissues become more permeable, which means fluid accumulates where it shouldn’t. Discussions have centred around beta human chorionic gonadotropin (hCG), oestrogen, prolactin, histamine, and prostaglandins, with substances that are active on blood vessels being connected.

It seems the exaggerated response of the ovaries is caused by luteinising hormone (LH), with hCG action also mimicking these changes. hCG has a follicle-stimulating hormone-like action in stimulating the ovaries, and sticks around in the body for quite a long time (long half-life). These effects mean hCG has a lot more to do with OHSS by itself. Bad timing also plays a role.

     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?

     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. It might be quite uncomfortable, but it will resolve itself. 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. 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.