Some women who use injectable fertility drugs get a mild form of OHSS, which goes away after a week. However, if pregnancy does occur, OHSS symptoms can get worse and last from several days to several weeks.
We know that the syndrome only appears in the presence of HCG. The picture is self-limiting and in the absence of gestation the patient returns to normal with the onset of menstruation.
In the case of gestation the levels of HCG (pregnancy hormone) rise and because of this the symptoms may worsen. Severe ovarian hyperstimulation syndrome (OHSS) is a serious complication. Symptoms are rapid weight gain, severe abdominal pain, severe nausea and vomiting, hypercoagulability (which can lead to blood clots in the legs or other locations), decreased urine output, and shortness of breath.
Severe ovarian hyperstimulation syndrome is very rare nowadays because we have the possibility of vitrifying embryos with very good results later on. For this reason, when a patient is at risk of hyperstimulation syndrome or has a mild hisper stimulation, she decides not to transfer the embryos in that cycle and to vitrify them in order to be able to transfer them later safely to the future mother.