Tuesday, 1 July 2014
Embryo culture involves incubating embryos till the time of their transfer into the uterus. After the appropriate method of fertilisation (IVF or ICSI) the eggs are left undisturbed in the incubator to allow the process of fertilisation to occur. There are accepted norms in identifying the days around embryo culture. The day of the pickup is called Day 0. The next day (when fertilisation is checked) is the first day of an embryo's life and this is called Day1. From here the days are counted serially.
Once fertilisation occurs, the genetic material carried by the egg and the sperm align together (the structure is called Pronucleus) and then fuse. In case the number of pronuclei is 3, these are abnormal in the amount of genetic material present in them and so these are discarded. The single cell of the embryo now starts dividing and the cell number (the cells of an embryo are called Blastomeres) starts increasing.
The ideal number of blastomeres is four on day 2 and eight on day 3. On the day 4 the embryo looks like a tight ball of cells. This day is a very dynamic stage and a lot of changes occur in the embryo. By the day 5, the cells have split into two groups, several of the cells align themselves on the periphery of the sphere that is covered by the egg shell - these ultimately play a role in implantation and form placenta. The others continue to stay in the form of a tight ball of cells at one pole of the embryo. These will ultimately form the baby. This stage of embryo on the day 5 of its life is called Blastocyst. Embryo transfer is typically done on the days 2, day 3 or day 5.