ABSTRACT

The reported incidence of ovarian hyperstimulation syndrome (OHSS) is extremely variable, according to different studies, because various classifications have been used. Furthermore, these studies relate to very different clinical situations such as controlled ovarian stimulation or ovarian stimulation during in vitro fertilization (IVF), which are not comparable in terms of therapeutic goals and strategies. When considering IVF treatment, the reported incidence lies between 3 and 6% for the moderate and between 0.1 and 2% for the severe form of OHSS1. The mild forms of OHSS, which have little clinical relevance, constitute about 20-33% of IVF cycles2. It has been estimated that, worldwide, at least 100-200 women suffer annually from severe OHSS per 100 000 cycles of assisted reproductive technologies (ART); there are about 500 000 IVF/ intracytoplasmic sperm injection (ICSI) cycles worldwide per year and probably as many if not more non-IVF cycles in which gonadotropins are used3,4. The largest cohort of OHSS cases was reported in Israel: the increase in incidence of the severe forms of OHSS surpassed the increase of total IVF activity during the same period (20-fold versus six-fold, respectively)5. Therefore, although the incidence of the severe form of OHSS is only about 1%, one should be aware of its recent, progressive increase. This constitutes a serious health hazard as well as a prophylactic challenge, since women treated with IVF/ICSI are a priori healthy young women. Moreover, there is a general unawareness of the syndrome among the lay public, which increases the risk for late or inappropriate diagnosis as well as its psychological impact on those who succumb to it.