Complications from fertility treatments are rare; nevertheless, some people do experience side effects. Anyone undergoing ovarian stimulation is at risk of developing ovarian hyperstimulation syndrome (OHSS), one of the most serious side effects of fertility treatments. Because if this, It’s to your advantage to be informed and on the lookout for symptoms to bring to your doctor’s attention

What is OHSS?

OHSS is irritation of the ovaries that can happen when they are stimulated to produce a lot of eggs at once. OHSS is caused by high levels of estrogen in the bloodstream, which causes the ovarian blood vessels to become leaky to fluids. This means fluids leave the bloodstream and collect in the abdominal cavity.

Even though a woman with OHSS drinks plenty of fluids, she can become severely dehydrated. As a result, the blood becomes thickened leaving her at risk for blood clots in the legs and lungs.

Read: Preparing for Your Egg Retrieval

What are the Symptoms of OHSS?

The symptoms of OHSS may be mild, moderate, or severe and usually begin four to five days following egg collection. The accumulation of fluid in the abdominal cavity can be very uncomfortable and cause bloating, sometimes breathlessness. In severe cases, the fluid enters the lungs and causes respiratory distress. This is why it’s very important to inform your doctor if you have any of the following symptoms:


Mild OHSS

  • Mild abdominal pain
  • Abdominal bloating and weight gain
  • Mild nausea
  • Vomiting
  • Diarrhea
  • Tenderness around the ovaries

Moderate to Severe OHSS

  • Rapid weight gain
  • Severe abdominal pain
  • Persistent nausea and vomiting
  • Decreased urinary frequency
  • Dark urine
  • Shortness of breath
  • Tight and enlarged abdomen
  • Dizziness

Mild or moderate OHSS usually resolves within a few days unless pregnancy occurs, which may delay recovery. Because the symptoms of OHSS are exacerbated by pregnancy, sometimes a “freeze all” cycle is the safest option. In this case, all the embryos are frozen and a transfer delayed until full recovery two or three months later.

Who is at risk?

Some women are more at risk than others of developing this complication. Women with polycystic ovaries are most at risk because they have many tiny follicles present that respond to the stimulation medicine. Other women at risk are those who have a high number of antral follicles, high anti-mullerian hormone (AMH) levels, high luteinizing hormone (LH) blood level and high LH to follicle-stimulating hormone (FSH) ratio.

An individual's risk should be assessed by a doctor ahead of starting an IVF cycle to adjust the starting dose of stimulation medication accordingly. Additionally, the doctor will do regular ultrasound scans of the ovaries during the stimulation phase and monitor the circulating estrogen levels as they rise.

If the blood estrogen level is rising too high or too quickly, the doctor can reduce the dose of FSH medication or "coast" the treatment by stopping the FSH injections for a few days. This will give the ovaries a break from being over-stimulated and help to reduce the chance of OHSS.

How common is OHSS?

Mild OHSS occurs in around 30% of all treatment cycles and is considered a normal side effect of ovarian stimulation for IVF. The symptoms are easily managed with over-the-counter painkillers, dietary changes, and increased fluid intake.

Severe OHSS affects around 3 to 8% of cycles and is managed well with medical help.

At-Home Treatment of Mild OHSS

Treatment usually involves keeping you comfortable until symptoms subside, which can take a week or longer if you are pregnant. Your doctor may also recommend:

  • Take over-the-counter pain relievers such as Tylenol.
  • Reduce activities — no heavy lifting and straining or strenuous exercise.
  • Maintain light activity.
  • Total bed rest could increase the risk of some complications.
  • Elevate your feet when resting. This helps your body get rid of the extra fluid.
  • Avoid sex until you feel better.
  • Abstain from alcohol and caffeinated beverages.
  • Drink plenty of clear fluids, 10 to 12 glasses a day. Drinks with electrolytes, such as Gatorade, are a good choice.
  • Record your weight twice daily and the number of times you urinate.
  • Contact your doctor if you note a 5-pound weight gain in 24 hours or a reduction in the frequency of urination by approximately 50%.
  • Be aware of bodily changes, and call the doctor with any nausea, pelvic pain or increasing symptoms.

Clinical Treatment of OHSS

For more severe cases, the following may be required:

  • Cancellation of embryo transfer until a later date
  • Prescription anti-nausea medication
  • Drain excess fluid from the abdomen with a needle puncture, similar to an egg retrieval
  • Administer intravenous fluids

How can OHSS be prevented?

Prevention is better than cure, and your doctor should monitor the stimulation phase of the IVF cycle carefully. Ultrasounds and blood tests measure the ovaries’ response to the stimulation drugs.

The dose will be lowered if the estrogen levels become too high or you may take a break from injections for a day or two. It is better to start with a lower dose and add extra FSH during ovarian stimulation than start too high and be at risk for complications. If the ovarian response is extremely high the doctor might choose to cancel the cycle altogether and start again with a lower dose next time.

Read: IVF Stimulation Protocols

Once a high ovarian response has been detected, a different type of trigger medication may be recommended. Usually an hCG trigger shot is taken when the follicles are big enough for egg retrieval, but if there is a risk of hyperstimulation the doctor may give you an agonist (Lupron) trigger before the egg collection to induce an LH surge (this can only be done in certain types of stimulation cycles where the patient has not been down-regulated with Lupron before the cycle started).

A lupron trigger will significantly reduce the chance of OHSS but may also reduce the number of eggs retrieved and may hamper the egg maturation process. If a Lupron trigger is used, a fresh embryo transfer cannot be done during that cycle because this type of trigger disrupts the uterine lining and there is a high chance of implantation failure. In this case, the embryos will be frozen and transferred another month.

Alternatively, a lower dose of hGC (for example half of the usual dose) can be used for trigger or a mixture of low dose HCG with Lupron can also reduce the risk of OHSS.

A study of all recently published data on OHSS by The Cochrane Collaboration had identified the following interventions as having at least a moderate benefit to preventing OHSS:

  • Metformin treatment before and during an IVF cycle for women with PCOS
  • Gonadotrophin-releasing hormone (GnRH) antagonist protocols for IVF cycles
  • GnRH agonist trigger in donor oocyte or for freeze-all cycles

Your doctor should be able to choose the best treatment regimen for you that minimizes the chance of complications while maximizing the treatment outcome.