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

results: The cryo-thawed blastocyst survival rate was similar between the PGD and IVF/ICSI groups (87% versus 88%, P ¼ 0.94). There was no significant difference in the implantation and clinical pregnancy rates between the two groups (35% versus 29%, P ¼ 0.45 and 34% versus 36%, P ¼ 0.77, respectively). During the same period, the multiple pregnancy rate in the fresh PGD programme dropped from 36% to 10% (OR ¼ 0.20, 95% CI 0.08 –0.48, P , 0.001) with no reduction in pregnancy rates.