A procedure still in the testing stage, where blastocysts (early stage embryos) are left longer in a culture to grow; therefore, allowing for only the best ones to be selected based on their growth and development in the lab. By implanting only two or three of the best blastocyts, this procedure minimizes multiple birth rates.
Embryos develop for 4 or 5 days (until they reach blastocyst stage), rather than the usual 2 or 3 days in IVF.
Transfer of a more developed embryo. It usually requires five days from the time of insemination of the eggs to reach this stage. Performing blastocyst transfer may allow the biologist to discriminate between healthy and unhealthy embryos, by allowing a longer observation period