Blastocoele collapse by micropipetting prior to vitrification gives excellent survival and pregnancy outcomes for human day 5 and 6 expanded blastocysts.

BACKGROUND

Manual puncture of the trophectoderm of human blastocysts with a needle before vitrification increases their survival rate, but the embryos take a long time to re-expand. This study examined whether causing human blastocysts to collapse by manual pipetting before vitrification would allow more rapid re-expansion and improve pregnancy rates.

METHODS

After embryo transfer in IVF cycles, surplus embryos that developed to the expanded blastocyst stage were placed in cryoprotectant and then artificially shrunk by mechanical pipetting with a fine hand-drawn glass pipette slightly smaller in diameter than the blastocyst. The shrunken embryos were placed in a small volume of vitrification solution and plunged into liquid nitrogen on a cryotop. The blastocysts were thawed by warming and then dilution in 1 mol/l sucrose.

RESULTS

Of 49 expanded vitrified blastocysts, 48 (98%) re-expanded within 3 h after warming. Following transfer (48 blastocysts in 28 cycles), 14 women (50%) became clinically pregnant, and the implantation rate was 33% (16/48). Eight healthy babies have been born in six deliveries, and the other eight pregnancies are ongoing. To date, there have been no spontaneous abortions.

CONCLUSIONS

The results suggest that artificial shrinkage with pipetting is a simple and effective technique to assist successful cryopreservation of expanded blastocysts by vitrification.