Ovarian hyper stimulation syndrome (OHSS)

Ovarian hyper stimulation syndrome or OHSS is a rare complication that results from stimulation during a fertility treatment. The manifestation of this syndrome can range from mild discomfort to, in rare cases, a serious illness for which hospitalization is required. Serious cases of OHSS are very rare. This information should serve the purpose of informing patients of the most serious problems and to ensure that patients do not become overly concerned if light symptoms appear. Careful planning is part of the stimulation treatment and it occurs under strict supervision. Nevertheless, it is not always possible to prevent overstimulation.

On the one hand, the process seeks to produce positive results for the patient and, on the other hand, the reaction of the body is personal and unpredictable.  Nevertheless, overstimulation is rare and can be well countered with practical or medicinal intervention.

How does ovarian hyper-stimulation syndrome manifest itself?

Different symptoms become apparent depending on the severity of the overstimulation. Precursors to these symptoms (ie. abdominal distention, nausea) can also appear during a normal stimulation process and require no treatment.

Moderate form


  • Discomfort and minor pain, nausea, bloating sensation, discovery of ascites via ultrasound

Severe form


  • Nausea, vomiting, diarrhea, oliguria (changes in urinary excretion), abdominal pain/upper abdominal pain, breathing difficulties, diaphragmatic stimulation, ultrasound showing enlarged ovaries and significant ascites, tension in the stomach as a result of the ascites

The possible symptoms listed above can be very frightening. It must be noted, however, that these symptoms do not appear without warning and, therefore, early counteractive measures can be taken. At the same time, the probability of severe OHSS occurring is very low at 0.1% to 2%.


Therapy for ovarian hyper-stimulation syndrome depends on its severity. In non-severe cases as well as in cases of light preliminary symptoms measures which can be applied at home are sufficient:  rest, increase in fluid intake (at least 3 to 4 liters per day), cool compresses on the abdomen (reduction of blood flow to the ovaries). A protein rich diet, as well as, protein drinks available in pharmacies (ie. Formitel) are also beneficial. If a severe form of OHSS occurs, outpatient care or hospitalization may be required. This can be administered either in the gynaecological department of the Goldenes Kreuz (for patients with private insurance) or in the gynaecological department of another hospital. In Vienna, the General Hospital (AKH) which is specialized in the treatment of OHSS and the SMZOst are recommended.

In the clinical setting there are a number of treatments available to combat the symptoms of OHSS and improve the well-being of the patient (intravenous fluids, boosting the renal excretion of water, puncture to reduce pressure). The constant monitoring of symptoms is also necessary for the prevention of complications (monitoring of fluid excretion, waist circumference, blood parameters etc.). This is to ensure the prevention of severe complications, such as kidney failure or thrombosis.

Emergence of ovarian hyper-stimulation syndrome

The reasons for the emergence of OHSS are not yet clear. Therefore, treatment can only be geared towards the symptoms of OHSS rather than its causes. What seems clear is the role of progesterone and human chorionic gonadotropin, which can occur at two points during the fertility treatment: Once during the hormonal stimulation and the second time at the onset of pregnancy. Therefore, pregnancy has a strengthening effect on existing OHSS. Analogous to this, two forms of OHSS have been distinguished: “early-onset” and “late-onset.” The ‘early-onset’ OHSS usually occurs within a few days of the puncture procedure. The symptoms and complications decrease at the latest with the next menstruation if pregnancy does not occur.

“Late-onset” OHSS is linked to hormone production at the onset of pregnancy and occurs about 8 to 17 days after the puncture procedure. It spontaneously improves with the reduction of progesterone (Corpus Luteum) activity which decreases in the 5th to 6th week of pregnancy.

Exemplary cases


Ms. F. notices stomach pains, bloating and a slight increase in abdominal girth a few days after the follicle puncture procedure. She is sometimes nauseous and has reduced appetite. An ultrasound determines that the ovaries are slightly enlarged and that fluid has collected in the abdomen. This condition lasts several days which Ms. F. spends in bed. She uses cold compresses and drinks a lot of fluids. She feels that this makes the symptoms more bearable. One week after the transfer, her menstruation sets in and her symptoms disappear. Unfortunately, she is not pregnant. Due to the strong response of her ovaries to stimulation it was possible to freeze several of the healthy embryos which gives her courage for a repeated attempt. 


12 days after the transfer was conducted in a fertility clinic, Ms. M. is admitted to the hospital with acsites (water collection in the stomach), respiratory distress, increased abdominal girth, and nausea. The patient reports that during the last 3-4 days has she begun to experience increasing discomfort, such as increased waist circumference and respiratory distress. Due to these complaints, Ms. M. is hospitalized. To alleviate breathing problems, a puncture is performed by which fluid is drained from the stomach area. This provides Ms. M. with some immediate relief. She also receives infusions; blood, urine, and her abdominal circumference is monitored regularly. The clinical signs and symptoms of OHSS begin to improve so that Ms. M. can be released from the hospital after 7 days. During her stay, it was determined that a pregnancy was achieved which was also the cause of the OHSS.

No permanent damage is expected from OHSS. This applies to the woman affected, and in case of a pregnancy, to the fetus. If you are unsure of the treatment required in the event of an occurrence of OHSS, please do not hesitate to clarify this with doctors at the fertility centre, over the emergency telephone line, or with the referred gynaecologists.