Spontaneous forms of OHSS may occur, but these are very rare and always reported during pregnancy.
The pathophysiology ofOHSS remains poorly understood, and there is no reliable test to predict which patients will develop severe OHSS. Human
chorionic gonadotropin (hCG) is thought to play a crucial role in the devel-
ulating hormone (FSH) receptor could be an essential prerequisite in the
development of spontaneous OHSS and could explain why symptoms in
spontaneous cases of OHSS appear later than in iatrogenic OHSS, in which
follicular recruitment and enlargement occur during the ovarian stimulation
with exogenous FSH. Smits et aL described a mutation in the FSH receptor gene in a patient presenting spontaneous OHSS during each of her four
etiologicalroleinthedevelopmentofOHSS.Thedataavailablesofar supportthenotionthatOHSSisaconsequenceofmultiplecorpora!urea formationassociatedwithactiveangiogenesisandincreasedcapillary permeability.