Should embryos be cultured on to day 6 following embryo transfer if there are no embryos suitable for cryopreservation on (2013)

Type of publication:
Conference abstract

*Hughes G.; *Binnersley S.; *Wallbutton S.; *Gittins V.; *Parry S.; *Hatton A.; *Lavender A.; *Kasraie J.

Human Fertility; 2013; vol. 16 (no. 3)

Introduction : Risks and costs associated with stimulation/egg collection mean that storage of excess viable embryos and maximisation of cumulative pregnancy rates from a single egg collection are a priority for clinics.  Should we culture all embryos not suitable for cryopreservation on day 3 (D3) and day 5 (D5) onwards to allow us to assess their viability for cryopreservation over an extended period? Materials and Methods: Retrospective  analysis of the development of 457 embryos from 89 patients that were allocated for training from D3 (n=71) and D5 (n=18) transfer patients that did not meet cryopreservation criteria on D3 (6C 15% fragmentation, 70 hours post insemination/injection) or D5 ( <= 3BB (Gardner and Schoolcraft) 118 hours post insemination). The  embryos allocated were cultured at 6% CO2 to D6 and graded each day. Results: Blastulation rates for D5 transfer patients were significantly greater than D3 transfer patients (43.04% vs 26.42%, p <= 0.0005). 1.88%  of embryos from D3 patients with 0 frozen developed to <= 3BB on D5 vs 8.57% of embryos from D3 patients with 1 frozen (p <= 0.0142). 6.29% of embryos from D3 patients with 0 frozen developed <= 3BB on D6 vs 11.43% of embryos from D3 patients with 1 frozen (p=0.1498). 11.39% of embryos from D5 transfer patients developed to <= 3BB on D6. Conclusions : This small retrospective study, in suboptimal culture conditions,  appears to show it may be beneficial to routinely culture embryos not meeting our cryopreservation criteria on D3 or D5 to D6. At present our biochemical success rates (53% vs 41%, p=0.3671) and clinical success rates for D5 vs D6 transfers (43% vs 32%, p=0.658) suggest that D6 blastocysts are as viable as D5 blastocysts. Practical
and financial implications must be taken into account but this practice may reduce ‘fresh’egg collections and maximise cumulative success, thereby reducing risk and cost to the healthcare economy.