The specifically prepared sperms and the incubated eggs are combined in a test tube or petri dish in prescribed number ratio and left for few hours for them to unite.
After 18 hours they are examined under stereo zoom microscope for fertilization which is obvious if two pronucleus are seen clearly. Each pronucleus denotes the de-condensation of male and female nucleus (DNA). Once they are identified, fertilization is confirmed. This day could be accounted as Day 1. Our IVF lab utilizes TRIGAS (O2, CO2, N2 mixture) incubator instead of CO2 alone, since the low Oxygen (5 % O2) improves the culture Conditions and integrity of embryos.
After 48 hours, properly growing embryos shows 4 cells inside, and after 72 hours they show 8 cell divisions. Only then they are considered as good embryos. Once the cell division seems to be insufficient and the embryos have odd number of cells and unequal cells they are considered to be “blocked” ones and they have meager chances to make blastocysts at the end of Day 5. Depending on the number of 8 cell stage embryos available on day 3, the type of embryo transfer and the day of embryo transfer are decided. The success rates are also destined according to the number of 8 cell staged, grade I embryos available in the culture system on day 3, for that particular couple.