(1) Women with an exaggerated response to ovarian stimulation medication
(2) Women with a history of ovarian hyperstimulation syndrome (OHSS)
When there is an increased response to ovarian stimulation medication (FSH and HMG) then there is an increased risk of one of the most troubling possible complications: ovarian hyperstimulation syndrome (OHSS). The abnormalities that cause OHSS and the treatments that effectively minimize the impact of OHSS are poorly understood.
Risk factors for OHSS include multiple smaller antral size follicles at the time of ovulation, polycystic ovarian syndrome (PCOS), rapidly and very high estradiol concentrations, younger age, thin body habitus, and exposure to hCG. This disorder generally lasts for 1-2 weeks and then spontaneously resolves.
Some of the clinical characteristics of OHSS are marked enlargement of the ovaries (that are very friable and easily damaged), increased permeability of the circulatory system (such that fluids leak from the capillaries of the blood vessels into “third spaces” inside the body to cause potentially very large pockets of free fluid and bloating), dehydration and kidney abnormalities (potentially including kidney failure) due to the massive loss of fluids from the circulatory system into third spaces, and difficulty breathing due to the collection of fluid around the lungs. OHSS can be a life threatening disorder.
There are many theories as to the physiological abnormality causing OHSS, with many researchers looking closely at vascular endothelial growth factor (VEGF) since it is known to increase vascular permeability, but no one to date has a reliable test or set of tests to predict who will develop OHSS.
The treatment of OHSS remains supportive management to maintain intravascular fluid volume (primarily with IV solutions), removal of excess fluid in the abdominal third spaces (ascites) that can restrict breathing (by causing pressure on the diaphragm at the base of the lungs), control of pain, and possibly give DVT prophylaxis.