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    Ovarian hyperstimulation syndrome


    Definition of Ovarian hyperstimulation syndrome

    Ovarian hyperstimulation syndrome may occur after using injectable hormone medications during in vitro fertilization (IVF), a treatment for infertility. Injectable fertility medications stimulate the development of eggs in the ovaries, but it can be difficult to tell exactly how much medication you might need.

    Too much of the hormone in your system can lead to ovarian hyperstimulation syndrome (OHSS), where your ovaries become swollen and painful. A small number of women may develop severe OHSS, which can cause rapid weight gain, abdominal pain, vomiting and shortness of breath.

    Less often, OHSS happens during fertility treatments using medications you take by mouth, such as clomiphene. Occasionally OHSS occurs spontaneously, not related to fertility treatments.

    Symptoms of Ovarian hyperstimulation syndrome

    Symptoms of ovarian hyperstimulation syndrome often begin within 10 days after using injectable medications to stimulate ovulation. Symptoms can range from mild to severe and may worsen or improve over time.

    Mild to moderate OHSS

    With mild to moderate ovarian hyperstimulation syndrome, symptoms can include:

    • Mild to moderate abdominal pain that may come and go
    • Abdominal bloating or increased waist size
    • Nausea
    • Vomiting
    • Diarrhea
    • Tenderness in the area of your ovaries

    Some women who use injectable fertility drugs get a mild form of OHSS, which goes away after about a week. If pregnancy occurs, however, symptoms of OHSS may worsen and last several days to weeks.

    Severe OHSS

    With severe ovarian hyperstimulation syndrome, you might have:

    • Rapid weight gain — such as 5 pounds (2.3 kilograms) in one day or 10 pounds (4.5 kilograms) in three days or more
    • Severe abdominal pain
    • Severe, persistent nausea and vomiting
    • Decreased urination
    • Dark urine
    • Shortness of breath
    • Tight or enlarged abdomen
    • Dizziness

    When to see a doctor

    If you’re having fertility treatments and you experience symptoms of ovarian hyperstimulation syndrome, tell your doctor. Even if you have a mild case of OHSS, your doctor will want to observe you for sudden weight gain or worsening symptoms.

    Contact your doctor right away if you develop breathing problems or pain in your legs during your fertility treatment. This may indicate an urgent situation that needs prompt medical attention.


    The cause of ovarian hyperstimulation syndrome isn’t fully understood, although having a high level of human chorionic gonadotropin (HCG) — a hormone usually produced during pregnancy — in your system plays a role. Ovarian blood vessels react abnormally to HCG and begin to leak fluid. This fluid swells the ovaries, and sometimes large amounts move into the abdomen.

    During fertility treatments, HCG may be given as a “trigger” so that a mature follicle will release its egg. OHSS usually happens within a week after you receive an HCG injection. If you become pregnant during a treatment cycle, OHSS may worsen as your body begins producing its own HCG in response to the pregnancy.

    Injectable fertility medications are more likely to cause OHSS than is treatment with clomiphene (Clomid, Serophene), a medication given as a pill you take by mouth.

    Risk factors

    Young women with polycystic ovary syndrome who have many follicles are at highest risk of ovarian hyperstimulation syndrome. Factors that increase your risk of OHSS include:

    • Polycystic ovary syndrome — a common reproductive disorder that causes irregular menstrual periods, excess hair growth and unusual appearance of the ovaries on ultrasound examination
    • Large number of follicles
    • Young age
    • Low body weight
    • High or steeply increasing level of estradiol (estrogen) before an HCG trigger shot
    • Previous episodes of OHSS
    • Migraine headaches
    • A multiple pregnancy

    In some cases, OHSS affects women who have no risk factors at all.

    Complications of Ovarian hyperstimulation syndrome

    About 1 to 2 percent of women undergoing ovarian stimulation develop a severe form of ovarian hyperstimulation syndrome. Severe OHSS can be life-threatening. Complications may include:

    • Fluid collection in the abdomen and sometimes the chest
    • Electrolyte disturbances (sodium, potassium, others)
    • Blood clots in large vessels, usually in the legs
    • Kidney failure
    • Twisting of an ovary
    • Rupture of a cyst in an ovary, which can lead to serious bleeding
    • Breathing problems
    • Pregnancy loss from miscarriage or termination because of complications
    • Rarely, death

    Tests and diagnosis

    For ovarian hyperstimulation syndrome, your doctor may make a diagnosis based on:

    • A physical exam. Your doctor will take note of any weight gain, increases in your waist size and abdominal pain you may have.
    • An ultrasound. If you have OHSS, an ultrasound may show that your ovaries are bigger than normal, with large fluid-filled cysts where follicles developed. During treatment with fertility drugs, your doctor regularly evaluates your ovaries with a vaginal ultrasound.
    • A blood test. Certain blood tests allow your doctor to check your blood concentration and whether your kidney function is being impaired because of OHSS.

    Treatments and drugs

    Ovarian hyperstimulation syndrome generally resolves on its own within a week or two or somewhat longer if you’re pregnant. Treatment is aimed at keeping you comfortable, decreasing ovarian activity and avoiding complications.

    Mild to moderate OHSS

    Mild OHSS typically resolves on its own. Treatment for moderate OHSS may involve:

    • Anti-nausea medication, prescription painkillers or both
    • Frequent physical exams and ultrasounds
    • Daily weigh-ins and waist measurements to check for drastic changes
    • Measuring how much urine you produce each day
    • Blood tests to monitor for dehydration, electrolyte imbalance and other problems
    • Drinking sufficient fluids
    • Draining excess abdominal fluid using a needle inserted in your abdominal cavity
    • Wearing support stockings to help prevent blood clots

    Severe OHSS

    With severe OHSS, you may need to be admitted to the hospital for monitoring and aggressive treatment, including intravenous (IV) fluids. Your doctor may give you a medication called cabergoline to lessen your symptoms. In some cases, your doctor may also give you another medication — known as a Gn-RH antagonist — to help suppress ovarian activity.

    Serious complications may require additional treatments, such as surgery for a ruptured ovarian cyst or intensive care for liver or lung complications. You may also need anticoagulant medications to decrease the risk of blood clots in your legs.

    Lifestyle and home remedies

    If you develop ovarian hyperstimulation syndrome, you’ll probably be able to continue your day-to-day routine. Follow your doctor’s advice, which may include these recommendations:

    • Try an over-the-counter painkiller such as acetaminophen (Tylenol, others) or ibuprofen (Advil, Motrin IB, others) for abdominal discomfort
    • Avoid sexual intercourse, as it may be painful and can cause a cyst in your ovary to rupture
    • Maintain a light physical activity level, avoiding strenuous or high-impact activities
    • Weigh yourself on the same scale and measure around your abdomen each day, reporting unusual increases to your doctor
    • Call your doctor if your signs and symptoms get worse


    To decrease your chances of developing ovarian hyperstimulation syndrome, you’ll need an individualized plan for your fertility medications. Expect your doctor to carefully monitor each treatment cycle, including frequent ultrasounds to check the development of follicles and blood tests to check your hormone levels.

    Strategies to help prevent OHSS include:

    • Adjusting medication dosage. Your doctor uses the lowest possible dose of gonadotropins to achieve the goals of stimulating your ovaries and triggering ovulation.
    • Coasting. If your estrogen level is high or you have a large number of developed follicles, your doctor may have you stop injectable medications and wait a few days before giving HCG, which triggers ovulation. This is known as “coasting.”
    • Avoiding use of an HCG “trigger” shot. Because OHSS often develops after an HCG “trigger” shot is given, alternatives to HCG for triggering ovulation are being studied as a way to prevent OHSS.
    • Freezing embryos. If you’re undergoing in vitro fertilization (IVF), all the follicles (mature and immature) may be removed from your ovaries to reduce the chance of OHSS. Mature follicles are fertilized and frozen, and your ovaries are allowed to rest for one or two cycles. You can resume the IVF process at a later date, when your body is ready.