Ovarian Hyperstimulation Syndrome

Ovarian hyperstimulation syndrome (OHSS) is a medical condition affecting the ovaries of some women who take fertility medication to stimulate egg growth. Most cases are mild.

Ovarian hyperstimulation syndrome, which may be abbreviated to OHSS, is an exaggerated response to excess hormones, usually the same as those taken for fertility treatments. It causes the ovaries to swell and leak fluid into the body, becoming painful and making the person feel tender and bloated.

As a side-effect, OHSS may occur when a patient is following a scheduled set of injectable hormone medications to stimulate the development of eggs in the ovaries. New protocols and strategies in place in fertility clinics have made the condition rare, however, except for very mild cases. It is also possible for OHSS to occur spontaneously and completely independently of any fertility treatments.

The causes of ovarian hyperstimulation syndrome are not fully understood. Experts believe that having a high level of human chorionic gonadotropin (hCG), which is a hormone usually produced during pregnancy, introduced to your body may play a part in its development. Ovarian blood vessels react abnormally to hCG and begin to leak fluid, which makes the ovaries swell. On some occasions, large amounts of this fluid may move into the abdomen.

There are several factors known to increase the risk of developing OHSS:

  • Being under the age of 35
  • Having a high or steeply increasing level of oestradiol (oestrogen) before an hCG trigger shot
  • Having a large number of follicles
  • Having a low body weight
  • Having had previous episodes of OHSS
  • Having polycystic ovary syndrome (PCOS)

On occasion, ovarian hyperstimulation syndrome will happen in patients who present no risk factors at all. 

As part of fertility treatment, hCG may be given as a “trigger” injection to encourage a mature follicle in a patient’s ovary to release an egg. Injectable fertility medications are more likely to cause OHSS than medication taken orally. 

If you become pregnant during a treatment cycle, OHSS may also worsen as your body begins producing its hCG in response to the pregnancy. The symptoms produced in this case may last between several days and several weeks.

Treatment of OHSS will depend on the severity of the condition for the individual patient. In some milder cases, it may simply improve on its own without medical intervention. On the other hand, more severe cases may require hospitalisation and further treatment. 

Knowing this is why it is important to ensure that any symptoms of OHSS that you have are checked by your doctor or healthcare provider as soon as possible. Any symptoms of the condition will usually begin within a week of using injectable medications for the stimulation of ovulation, though they may also take two weeks or longer.

Mild to Moderate Symptoms

In mild to moderate cases of ovarian hyperstimulation syndrome, the symptoms that may be experienced include:

  • Abdominal pain (mild to moderate in terms of feeling)
  • Abdominal bloating or an increased waist size
  • Diarrhoea
  • Nausea
  • Tenderness around the ovaries
  • Vomiting

Severe Symptoms

With severe ovarian hyperstimulation syndrome, it is possible to experience:

  • Abdominal pain (severe in terms of feeling)
  • Blood Clots
  • Decreased urination
  • Rapid weight gain (more than 1 kg) in 24 hours
  • Severe, persistent nausea or vomiting
  • Shortness of breath
  • Tightness or an enlarged abdomen

If you are undergoing fertility treatment and you are experiencing symptoms of OHSS, you must tell your doctor or healthcare provider right away. Even if the case is proven to be mild, they may wish to observe you for sudden weight gain or other worsening symptoms.

You must contact your doctor immediately if you develop breathing problems or experience pain in your legs during fertility treatment. This may indicate that you require urgent medical attention.