So, the big question. When do you transfer these beautiful embryos? There is the school of thought that advocates for allowing the embryos mature, in order to identify the more viable ones with a greater chance of survival. Under this scenario, the embryos are allowed to mature up to blastocyst stage, i.e. 5 (or even 6) days post fertilisation. The other school of thought advocates for these embryos to be transferred to the uterus as quickly as possible, as it is believed this is their natural environment and the embryos will thrive better there. Under this scenario, the embryos are transferred 2 or 3 days post fertilisation. Now which is the better option? The jury is still out on this one. I can only share my own personal experience and opinion.
Prior to my 1st cycle, I had read so much pro-blastocyst literature that I was convinced that was the only approach for me. I paid the required premium at Nordica, and proceeded to allow my embryos mature till day 5 before undergoing transfer. From day 1 to day 3, my eggs were A+ quality, recording text book cell division at the right time. But from day 4, the story changed. And by day 5, instead of having all blastocysts, all I had was 1 blastocyst, with the rest being just morulas. So we transferred the sole blastocyst, along with 2 morulas. That cycle failed.
During cycle 2, this time at Georges Memorial, I emphatically stated that I would like my embryos to get to blastocyst stage before transfer. But Dr. Iketubosin told me something very interesting. He said that very few hospitals in Nigeria have the right medium to bring embryos to blastocyst stage. After day 3, the medium of the embryos is to be changed to a more advanced culture. But apparently, a lot of hospitals in Nigeria are not able to create a suitable enough culture, for a variety of reasons. They might promise you this, but are really not able to sustain in. This made a lot of sense to me, considering the sharp dip in the quality of my embryos after day 3. He advised that we opt not even for a day-3 transfer, but instead a day-2. I was extremely nervous about this prospect. Everything I knew up till that point implied that early embryo transfers almost never worked. But I trusted him, so I agreed. On the evening of day-2, 4 A+ embryos were transferred. That was an incredibly successful cycle!
Hospitals in more advanced places in the world are better able to cultivate the appropriate blastocyst culture. So in such places, it is all a matter of choice and preference.