Ovarian Hyperstimulation Syndrome (OHSS) occurs as a result of over response of the ovaries to stimulation. OHSS is a risk of assisted reproduction treatments (ART).
FSH is a natural hormone that stimulates the ovaries into producing an egg each month. Normally about twenty follicles are stimulated but one becomes dominant and the others die off. When a patient undergoes an IVF cycle she is given FSH which stimulates the ovaries into allowing all the possible follicles (& eggs) to develop.
OHSS occurs where the patient’s ovaries over responded to the medication. They are enlarged and fluid ‘weeps’ into the abdominal cavity (and sometimes the chest as well). We assess this by the patient’s history and by ultrasound assessment.
- The patient may complain of breathlessness and be breathless; she may require the use of a pillow to prop herself up at night in order to sleep.
- Pain and swelling in the abdomen. As fluid builds up in the abdomen the patient will experience a feeling of bloatedness.
- Nausea. The patient may feel sick and may even vomit.
- Feeling faint
- A decrease in the amount of urine being passed.
Identifying the patients who are at risk of OHSS is crucial. All patients who embark on an IVF cycle have an ultrasound assessment to check for polycystic ovaries because patients who have PCOS present a higher risk of developing OHSS. These patients are therefore monitored very closely and the dose of FSH they are prescribed is usually less than those without PCOS. Bear in mind that 30% of patients with PCOS have no physical symptoms so ultrasound assessment is very important in identifying patients at risk.
About 4% of women undergoing an ART cycle are likely to develop one or more of the symptoms listed above. Monitoring in these cases is particularly important. The patient may be asked to rest and in some cases, the treatment cycle may have to be cancelled. However, the management of the condition does not always call for the cancelling of a cycle. Once the symptoms have been identified the doctor may be able to advise a patient to ‘coast’ that is allowing the patient to continue developing follicles while removing the stimulation drug from her treatment regime. A patient can coast for several days with frequent blood tests to assess her response. Treatment may then go ahead if the doctor is happy with the patient’s progress. In general terms, patients who coast are generally successful in getting pregnant.
In some cases where a patient remains symptomatic, she may still have her egg retrieval but be advised to have an elective freeze. This means that the embryos are not transferred but are frozen for future use. In this instance the patient has time to overcome the stimulation and have the embryos transferred when she is feeling better. This decision to freeze would be made by the doctor if it is in the patient’s best interest.
If a patient is not feeling better and still retains a significant amount of fluid, the fluid can be drained. This may need to be carried out several times. Ideally it is carried out vaginally because this method allows the fluid to be removed easily. Most importantly this out-patient management usually allows the patient to avoid hospital admission. If a patient does undergo fluid drainage, she will usually feel enormous relief immediately afterwards.
Over the next few days, urinary output will be measured, as well as her weight and abdominal girth. She will phone the clinic each day to report on how she is feeling and is monitored very closely. If the patient is feeling unwell, the clinic has an emergency contact number where a member of the medical team can be contacted at any time.
Although OHSS is rare, it is extremely important that a patient raise any concerns she may have sooner rather than later so if it is a cause for concern it can be treated immediately and effectively.