Reduction of the multiple pregnancy rate in a preimplantation genetic diagnosis programme after introduction of single blastocyst transfer and cryopreservation of blastocysts biopsied on day 3.

BACKGROUND: An elective single-embryo transfer (SET) policy has not been applied to preimplantation genetic diagnosis (PGD) for inherited genetic disorders because of concerns regarding post-thaw survival of biopsied embryos. Our objective was to evaluate the survival and pregnancy potential of embryos biopsied for PGD at the cleavage stage and cryopreserved at the blastocyst stage and its contribution to the overall success of an elective SET policy in a PGD programme.

METHODS: From January 2006, all couples who had two or more transferable PGD blastocysts biopsied on Day 3 of culture were offered single-blastocyst transfer (SBT) and cryopreservation of surplus blastocyst(s) using a slow-freezing technique. We compared the outcome of 32 cryo-thawed PGD cycles with that of 191 cryo-thawed conventional in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) cycles performed between January 2006 and July 2008. We also compared the outcome of all fresh PGD cycles performed before and after January 2006.

RESULTS: The cryo-thawed blastocyst survival rate was similar between the PGD and IVF/ICSI groups (87% versus 88%, P = 0.94). There was no significant difference in the implantation and clinical pregnancy rates between the two groups (35% versus 29%, P = 0.45 and 34% versus 36%, P = 0.77, respectively). During the same period, the multiple pregnancy rate in the fresh PGD programme dropped from 36% to 10% (OR = 0.20, 95% CI 0.08-0.48, P < 0.001) with no reduction in pregnancy rates.

CONCLUSIONS: The survival and implantation potential of biopsied PGD embryos cryopreserved at the blastocyst stage is comparable to that of non-biopsied IVF/ICSI cryopreserved blastocysts. Elective SBT and cryopreservation of surplus blastocysts for later use should extend to include PGD for inherited genetic disorders.