In standard IVF/ICSI, embryos are grown under very strictly controlled conditions in the laboratory for two or three days. They are then transferred into the woman’s uterus (womb) and any additional embryos can be frozen for future use. Blastocyst culture refers to growing the embryos in the laboratory for two or three more days at which point they grow from 8 cells to 100 cells if embryos are good quality are referred as blastocyst embryos. Blastocyst transfer simply means that the blastocyst embryos are transferred to the woman’s uterus on day 5 or day 6 in exactly the same way that day 3 embryos are. Advantages of blastocyst culture and transfer
The human body is the best incubator for human embryos but if there are several embryos to choose from on day 3, we know that not all will survive to day 5 or day 6 whether they are in the laboratory or the womb. Keeping the embryos in the laboratory for these two extra days eliminates the possibility of transferring a (healthy-looking) embryo on day 3 which would naturally perish before day 5 or day 6.
The best advantage of Blastocyst transfer to prevent multiple pregnancy and birth. Therefore it gives a better chance of transferring an embryo which will lead to a successful pregnancy and birth.
For PGD it is better to do embryo biopsy on Blastocyst.