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Ovarian hyperstimulation syndrome (OHSS) is a complication occasionally seen in women who take certain fertility medicines that stimulate egg production (during ovulation induction). OHSS is the most serious complication that can arise from the use of infertility medications. Ovarian hyperstimulation syndrome can usually be predicted before it occurs although occasionally it can occur when minimal risk factor exists.

Normally, a woman produces one egg per menstrual cycle (per month). Some women undergoing fertility treatments are given medicines to help normalize egg development or increase egg production. However, if the drugs stimulate the ovaries too much, the ovaries can suddenly become very swollen and fluid can leak into the belly and chest area. This is called ovarian hyperstimulation syndrome (OHSS). OHSS occurs only after the eggs are released from the ovary (ovulation).

Most often OHSS is noted if ovulation induction done with human chorionic gonadotropin (hCG) to help trigger ovulation. You may have an even greater risk of this syndrome if you receive more than one dose of hCG after ovulation and if you become pregnant during this cycle. OHSS rarely, if ever, occurs in women who only take fertility medicines by mouth.

OHSS affects up to 10% of women who go through in vitro fertilization. In most cases the condition is mild, but some women get a severe and dangerous form of OHSS.


OHSS risk factors

  • Age younger than 35;
  • Very high estrogen level while undergoing fertility treatments – high estradiol levels, especially when associated with numerous small follicles on ultrasound;
  • Polycystic Ovarian Syndrome (PCOS);
  • Previous history of ovarian hyperstimulation syndrome.

When ovarian hyperstimulation syndrome should be expected

Ovarian Hyperstimulation Syndrome is when a woman’s ovaries become excessively enlarged as a result of hormone therapy that stimulates the development of follicles and prompts ovulation. OHSS could be expected:

  • During ovulation induction with gonadotropins – this treatment should be carefully monitored by checking blood levels of estradiol and ultrasound.
  • After follicles are mature, the woman could be given a high dose of injection (most often human chorionic gonadotropin – hCG) to trigger ovulation.
  • If doctors did not adjust the dosages of the stimulants to prompt an adequate number of eggs to reach maturity. In general doses are carefully adjusted on the basis of a woman’s response to the hormones but it’s a fine balancing act.
  • Even with excellent monitoring, there could be a very quick, adverse response to stimulation and cycles of reproductive therapies are sometimes cancelled prior to the injection of hCG.
  • hCG can be withheld if a woman’s response to the gonadotropins is excessive.

Ovarian hyperstimulation syndrome symptoms

Ovarian hyperstimulation syndrome can occurs only after ovulation – after release of the egg from ovary. If the drugs stimulate the ovaries too much, the ovaries can suddenly become very swollen and fluid can leak into the belly and chest area. OHSS affects up to 10% of women who go through in vitro fertilization. In most cases the condition is mild, but some women get a severe and dangerous form of OHSS.

Most women with OHSS have mild symptoms such as:

OHSS types

  • Abdominal bloating,
  • Pelvic discomfort, nausea, dizziness,
  • Mild pain in the abdomen,
  • Weight gain.

In rare cases, women with OHSS can have more serious symptoms, including:

  • Significant weight gain (more than 10 pounds in 3 – 5 days),
  • Severe pain or swelling in the abdomen,
  • Decreased urination,
  • Shortness of breath about 7-10 days after oocyte retrieval.

Ovarian hyperstimulation syndrome – exams and tests

If you have a severe case of OHSS, your health care provider will need to carefully monitor your symptoms. You may be admitted to the hospital.

Your weight and size of your belly area (abdomen) will be measured. Tests that may be done include:

  • Abdominal ultrasound or vaginal ultrasound,
  • Chest x-ray,
  • Complete blood count,
  • Electrolytes panel,
  • Liver function test,
  • Tests to measure urine output.

OHSS treatment

Mild cases of OHSS usually don’t need to be treated. In most cases the discomfort and OHSS symptoms could be reduced by doing the following:

  • Get plenty of rest with your legs raised. This helps your body release the fluid. Light activities are better than complete bed rest, unless your doctor tells you otherwise.
  • Drink at least 10 – 12 glasses of fluid a day (especially drinks that contain electrolytes).
  • Avoid alcohol or caffeinated beverages (such as colas or coffee).
  • Avoid intense exercise and sexual intercourse, which can cause ovarian discomfort and may cause ovarian cysts to rupture or leak or cause the ovaries to twist and cut off blood flow (ovarian torsion).
  • Take an over-the-counter pain reliever such as acetaminophen (Tylenol).

It is important to weigh yourself each day to make sure you are not putting on too much weight (5 or more pounds a day).

In the rare case that you develop severe OHSS symptoms, you will probably need to go to the hospital.

In most cases the OHSS symptoms will go away on their own after period/menstruation starts.

If you become pregnant during OHSS, the symptoms may get worse and can take weeks to go away.

Ovarian hyperstimulation syndrome – possible complications

In very rare cases when ovulation induction was not properly monitored or if the female body overreacted to normal doses of the medication, the OHSS can lead to life-threatening complications, including:

  • Blood clots,
  • Kidney failure,
  • Severe electrolyte imbalance,
  • Severe fluid build-up in the abdomen or chest.

You need to contact your doctor immediately if you experience any of the following symptoms:

  • Excessive weight gain (more than 5 pounds a day),
  • Severe abdominal pain,
  • Nausea so intense that you can’t keep food or liquids down,
  • Decreased urination,
  • Shortness of breath,
  • Dizziness.

Ovarian hyperstimulation syndrome – prevention

Adequate and careful monitoring during ovulation induction is crucial. Blood tests and pelvic ultrasounds should be done regularly to make sure that ovaries aren’t over-responding.

If estrogen level rises very high or very quickly while taking fertility injections, your risk for ovarian hyperstimulation syndrome is increased. You may need to take a lower dose of the medicines or temporarily stop treatment.

Some women may be given a protein solution called albumin to reduce the chances of ovarian hyperstimulation syndrome.

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