Ovarian hyperstimulation syndrome (OHSS) is a rare complication of ovarian stimulation during infertility treatments.
During IVF treatment the ovaries are stimulated by daily hormone injections to retrieve enough number of eggs. However, the unpredictable response of the ovaries to ovulation induction makes the prediction and prevention of OHSS difficult. Hence, heightened clinical suspicion and early intervention of OHSS are paramount to the reduction of morbidity and mortality.
Ovarian stimulation for IVF is associated with up to a 5% risk of severe ovarian hyperstimulation syndrome. Human chorionic gonadotrophin (hCG) is given as a "trigger" so that a mature follicle will release its egg.
OHSS usually happens within a week after receiving an hCG injection. If pregnancy occurs during that treatment cycle, OHSS may worsen as the body also begins producing its own hCG in response to the pregnancy.
OHSS is characterized by ovarian enlargement due to multiple ovarian cysts and an acute fluid shift into the extravascular space. Complications of OHSS include ascites, hemoconcentration, hypovolemia, and electrolyte imbalances.
Early-onset OHSS: Early-onset OHSS developes in less than 10 days from egg collection, and related to ovarian stimulation protocols and hCG trigger shot.
Late-onset OHSS: Late-onset OHSS developes 10 days after egg collection, and related to endogenous hCG production from the pregnancy.
The cause of ovarian hyperstimulation syndrome is not fully understood. Having a high level of human chorionic gonadotropin (hCG) — a hormone usually produced during pregnancy — introduced into the 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.
OHSS is generally self-limiting and conservative. It is a manageable disease. Pregnancy may cause symptoms to persist for a longer period of time. The key point in the management of OHSS is the correct management of patients. For this, it is important first of all to determine the stage of the disease.
With mild to moderate ovarian hyperstimulation syndrome, symptoms can include:
To decrease the risk of developing ovarian hyperstimulation syndrome, an individualized plan for fertility medications is needed.
Fortunately, with the prevention strategies, in particular with the increased utilization of GnRH-antagonist cycles, GnRH-agonist-only or dual hCG/GnRH-agonists triggers, and elective freeze-all cycles, and carefully monitoring the treatment cycle, including frequent ultrasounds to check the development of follicles severe OHSS has become increasingly rare in most IVF clinics.
In PCOS women injectable fertility drugs generally causes a mild to moderate form of OHSS. This usually goes away after about a week. But, if pregnancy occurs, symptoms of OHSS may worsen and last several days to weeks.
Even if it is a mild case of OHSS observation for sudden weight gain or worsening symptoms is necessary. The developement of breathing problems or pain in the legs during the fertility treatment may indicate an urgent situation that needs prompt medical attention.
Indeed, mild OHSS patients can be treated as an outpatient, while severe and critical OHSS patients have an indication for hospitalization (sometimes even intensive care conditions).