What Is Ovarian Hyperstimulation Syndrome

Ovarian hyperstimulation syndrome (OHSS) refers to the complications that occur as a result of fertility medications given to stimulate or mimic ovarian function. These side effects can be categorized into mild, moderate, or severe, depending on the symptoms experienced by the patient.

Ovarian hyperstimulation syndrome (OHSS)

With IVF success in the Philippines increasing alongside advances in medical technology, assistive reproductive technology has also increased. Today, reproductive therapies feature a host of different modalities. OHSS is frequently associated with the administration of human chorionic gonadotropin (hCG), although estrogen, estradiol, prolactin, histamine, and prostaglandins have been implicated in previous cases. Under normal circumstances, this hormone triggers final oocyte maturation, followed by ovulation. Women who have low levels of this hormone may receive a single injection to trigger ovulation, but may receive multiple doses after ovulation as well as during pregnancy.

Ovarian hyperstimulation syndrome usually develops several days after oocyte retrieval for in-vitro fertilization, or after assisted ovulation. Human chorionic gonadotropin activity on the blood vessels within the ovaries is similar to the effects exerted by LH, and also stimulates the ovaries in a way similar to the action of FSH. Exogenous hCG is also more likely to result in OHSS than hCG produced by the body.

Some of the symptoms include enlargement of the ovaries due to the presence of multiple ovarian cysts, as well as fluid shifting into the extravascular space. The latter symptom presents as abdominal swelling, and is associated with several complications, such as electrolyte imbalances and even hemoconcentration and associated low blood volume in circulation.

The three grades of severity for ovarian hyperstimulation syndrome are as follows:

  • Mild OHSS
    • Grade 1 – abdominal distention and discomfort.
    • Grade 2 – grade 1 plus gastrointestinal symptoms of nausea, vomiting, or diarrhea, plus ovarian enlargement of 5-12 cm (seen during ultrasound).
  • Moderate OHSS
    • Grade 3 – Mild OHSS plus ascites evident on ultrasound.
  • Severe OHSS
  • Grade 4 – features of moderate OHSS plus evidence of ascites upon physical examination, fluid in the thoracic cavity, and dyspnea (difficulty breathing).
  • Grade 5 – grade 4 plus change in blood volume, increased blood viscosity as a result of hemoconcentration, coagulation abnormalities, and diminished renal blood flow and function.

The incidence of OHSS among has been estimated to occur at the following rates:

  • Mild: 8-23%
  • Moderate: 1-7%
  • Severe: 0.25-5%

Thankfully, the prognosis for OHSS is excellent for mild and moderate cases, and if severe cases are given the appropriate treatment, prognosis remains optimistic for such cases as well.

Addressing infertility in the Philippines is an important issue, and with more women turning to assistive reproductive technologies, it is important for patients as well as physicians to be aware of OHSS. It is important that patients keep track of their weight, drink plenty of water, and measure their abdominal girth regularly. Physicians must instruct their patients on exogenous hCG therapy to report bloating, abdominal discomfort, and any changes in their urine output.