Can we eliminate severe ovarian hyperstimulation syndrome? Not completely

Sir, It is with great interest that we read Dr Orvieto's article ‘Can we eliminate severe ovarian hyperstimulation syndrome?’ (Orvietto, 2005). Of course, as cases of spontaneous ovarian hyperstimulation syndrome (OHSS) have continued to be reported in the literature since the 1990 s (Ayhan et al., 1996) and possibly earlier (O'Loughlin and Brookes, 1987), we will never be able to completely eliminate OHSS. Nevertheless, Dr Orvietto and his co-workers should be commended on developing a clinical algorithm to reduce the risk of severe OHSS following ovarian stimulation. The use of GnRH agonists to induce a gonadotrophin surge in the place of hCG is not new (Buckett et al., 1998) and it is wrong to suggest that its use will almost totally eliminate severe OHSS. Reports in the early 1990s (Bentick et al., 1990; van der Meer et al., 1993) demonstrated that GnRH agonists do not prevent OHSS—even in non-conception cycles. We believe that immature oocyte retrieval and in vitro oocyte maturation (IVM) without any ovarian stimulation at all is a more reliable way to reduce the risk of OHSS in women with polycystic ovaries who are at risk and yet maintain a reasonable pregnancy rate (Chian et al., 2000). In women with normal ovulatory ovaries, the combination of natural cycle IVF with IVM (Chian et al., 2004) will similarly lead to a reduced risk of OHSS—even if GnRH agonists are substituted for hCG in ‘at risk’ women. In our experience so far, we have performed over 500 cycles of conventional IVM or natural cycle IVF combined with IVM without any cases of OHSS and have achieved clinical pregnancy rates of 30–40% in women aged <40 years of age. The only way to avoid iatrogenic OHSS is to avoid ovarian stimulation.