Depending on the concentration, motility and morphology of spermatozoa, classical IVF or ICSI is employed. After insemination, eggs are incubated for a period of 24 hours, after which fertilization rate and a number of pronuclear stage (PN) embryos are determined. At this stage, an egg is successfully fertilized and two pronuclei are seen in the cell, representing chromosomes from the mother and the father. Over the next day, the embryos will be left to develop. Meanwhile, it is best to have as little contact with the embryos as possible, because when the embryos are removed from the incubator, crucial conditions, such as: humidity, concentration of gases and temperature change can affect their development. On the third day post egg collection, one of our embryologists will call to inform you about the progress of fertilization, quality of day 3 embryos (comprised of 6-8 cells) as well as advantages and eligibility criteria of culturing embryos till day 5 for a blastocyst transfer. The embryonic genome is activated after the 6-8 cell stage, therefore, if the conditions allow, extended culture will highlight embryonic arrest and help identify healthy embryos for transfer, though not all embryos that develop until day 5 will be chromosomally normal. If a guarantee of healthy embryos is needed then we must perform pre-implantation genetic diagnosis (PGD).
We will weigh up the pros and cons of each option and decide together whether we will proceed with a transfer of day 3 embryos or day 5 blastocysts.
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