First, only approximately half of the preimplantation embryos reach the blastocyst stage.

In the newer procedure, the embryos are allowed to grow for five days until they reach the blastocyst stage.

It has usually reached the blastocyst stage at the time of implantation.

Single or sequential medium are equally effective for the culture of human embryos to the blastocyst stage.

Early development following the blastocyst stage is extremely rapid.

Placentation occurs two weeks after mating, with the blastocyst stage lasting seven to eight days.

The four cells had been carefully separated, and each one allowed to divide to the blastocyst stage.

After fertilization, the embryos were grown in a laboratory for five days, to the blastocyst stage containing 100 or more cells.

Human embryos reach the blastocyst stage 4-5 days after fertilization.

Most of the rest die very early: only about 20 percent of the embryo clones make it to the blastocyst stage.