Analysis of oocyte cryopreservation in assisted reproduction: the Italian National Register data from 2005 to 2007

This paper reports on oocyte cryopreservation efficacy in Italy with respect to successful IVF from 2005 to 2007, presenting data from 193 centres collected by the Italian National Register. Post-thawing survival rates, number of transferred embryos, implantation rates and clinical pregnancy rates per transfer with respect to frozen/vitrified oocytes (FVO) were analysed. These numbers were compared with those obtained using frozen embryos or fresh oocytes. A total of 121,708 cycles were initiated, of which, 7.1% (8682) were FVO cycles and 2.4% (2952) were frozen embryo cycles. Of the 81,786 FVO, 52.5% (42,917) were thawed and 26.9% (22,005) inseminated. Of those inseminated, 68.0% (14,966) yielded good embryos. These numbers were significantly lower than those using fresh oocytes in which 77.9% (197,242; fresh oocytes versus FVO P < 0.001) of inseminated oocytes generated good embryos. Implantation rate using FVO was 6.9%, which was significantly lower than that using fresh oocytes (13.5%; P < 0.001) and frozen embryos (8.8%; P < 0.001). Pregnancy rate per transfer using FVO was 12.5% and significantly lower than that using fresh oocytes (24.9%; P < 0.001) or frozen embryos (16.4%; P < 0.001). There were 505 deliveries after IVF with FVO and 582 babies.