Type of publication:
*Nash K.; *Gittins V.; *Hatton A.; *Binnersley S.; *Hughes G.; *Kasraie J.
Human Fertility; 2013; vol. 16 (no. 3)
Introduction : Following the HFEA's 'Multiple Birth, Single Embryo Transfer Policy'in 2008, blastocyst culture has become routine practice in many clinics. In our clinic, patients unable to transfer on day 5 (D5) due to failed blastocyst development or poor quality, are cultured to day 6 (D6). Supernumerary embryos not suitable for freezing on D5 are cultured to D6 and frozen if viable. We compared biochemical and clinical pregnancy rates for D5 and D6 blastocyst transfers to determine whether routine culture to D6 is beneficial. Method: Biochemical (BPR) and Clinical (CPR) pregnancy rates were compared for D5 and D6 transfers between 01/01/09 and 31/05/12. Results were analysed using Fisher's Exact test . We distinguished D6 blastocysts that were 'true'D6 from those that might have been later developing D5 blastocysts. Results: There was no significant difference in BPR (51.7%) and CPR (41.4%) for D5 (n=203) and D6 (43.5% and 30.4%, n=23) (BPR p=0.51, CPR p=0.37). One patient definitely had a 'true'D6 blastocyst. Conclusion: Culture to D6 appears beneficial as D5 and D6 pregnancy rates are similar. However, small numbers mean the D6 group results may be unreliable. One patient out of 23 had a definate D6 blastocyst making it possible that the other 22 developed late on D5. To truly distinguish D5 and 6 blastocysts we could perform transfers later on D5, but this may be impractical, particularly with blastocysts developing after 5 pm. Alternatively time-lapse technology would allow precise timing of blastulation. With these results in mind, it is likely that our policy of culturing to and freezing blastocysts on D6 regardless of the day of transfer is beneficial and will improve cumulative pregnancy rates. The number of fresh cycles a patient requires will also be reduced, ultimately benefiting the patient through reduced risk/cost, and the clinic/NHS healthcare economy.*