Читать книгу Assisted Reproduction Techniques - Группа авторов - Страница 149

The GnRH antagonist cycle is now widely recognized as superior to the agonist cycle in reducing the risk of OHSS in women with polycystic ovaries [8]. With equivalent pregnancy rates, the adoption of this strategy appears unquestionable. It is also prudent to consider the option of using a GnRH agonist trigger instead of hCG to further reduce OHSS rates in those at risk.

In a meta‐analysis of studies looking at agonist versus antagonist protocols for pituitary suppression during IVF, the GnRH antagonist protocols were associated with a reduced risk of OHSS (OR 0.61, 95% CI 0.51 to 0.72; 36 RCTs; n = 7944; moderate quality evidence) whilst not compromising the live birth rate (OR 1.02, 95% CI 0.85 to 1.23; 12 RCTs; n = 2303; moderate quality evidence) [8].

The GnRH antagonist cycle also allows the use of GnRH agonist rather than hCG as the pre‐ovulatory trigger further reducing the risk of OHSS (OR 0.15, 95% CI 0.05 to 0.47; eight RCTs, 989 women; moderate‐quality evidence) [9]. However, the use of a GnRH agonist in this way may be associated a lower live birth rate due to a deficient luteal phase (OR 0.47, 95% CI 0.31 to 0.70; five RCTs, 532 women, moderate‐quality evidence) [9]. Two approaches have been suggested to overcome the luteal phase deficiency – supplementation with exogenous estrogen and progesterone in the luteal phase or rescuing the corpus luteum using low dose hCG given either alongside the GnRH agonist trigger or on the day of the oocyte retrieval. Use of modified luteal phase support appears to lead to similar live birth rates with a GnRH agonist trigger as with hCG (OR 0.84, 95% CI 0.62 to 1.14; five RCTs; n = 857) [10].

An alternative approach has been elective cryopreservation of embryos following oocyte retrieval, followed by transfer in a frozen embryo transfer cycle – the “segmentation” approach [11]. A recent multicenter trial including 1508 women found that the segmentation approach led to a higher live birth rate (49.3% vs. 42.0%; RR 1.17, 95% CI 1.05 to 1.31) with a lower risk of OHSS (1.3% vs. 7.1%, RR 0.19, 95% CI, 0.10 to 0.37), but a higher risk of pre‐eclampsia (4.4% vs. 1.4%, RR 3.12, 95% CI, 1.26 to 7.73) [12].

New concepts include the possibility of using Kisspepetin as the pre‐ovulatory trigger [13], which has generated much interest. It is also possible to use dopamine agonists, such as cabergoline, to inhibit phosphorylation of the receptor for VEGF, which has also been shown to reduce the incidence of OHSS [14]. There is the possibility to consider in vitro maturation (IVM) of oocytes collected from unstimulated or minimally stimulated ovaries, although this requires particular expertise in the clinic and laboratory, and despite some clinics demonstrating success with this approach it has not gained widespread popularity [15].