Our IVF Lab

CTTBC (Caree Test Tube Baby Center) IVF lab have been carefully assessing embryos on the first day after egg retrieval at the zygote, or 1-cell embryo stage. We use morphologic parameters of the pronuclei on day one as part of the overall embryo quality assessment, and also as part of their selection criteria for the best embryos to transfer. This assessment on day one is an interesting and possibly useful tool. By 48 hours ("day 2"), the embryos must be to at least 2 cells - or they have "arrested". We prefer that at least some of them are at the 3 or 4 cell stage by then.

By 72 hours ("day 3"), we like to see at least 6 cells - and preferably some at about 8 cells. We have seen babies that came from 4 cell embryos on day 3, but chances for pregnancy increase significantly with increasing cell number.

Embryos with higher cell numbers, regular appearing cells and little or no fragmentation have a higher overall chance of implanting than do other embryos with less cells, more irregularity and significant fragmentation.

Ultimately, the true test of embryo quality is whether it implants and develops normally and eventually goes home from the hospital with mom and dad. In other words, embryo grading systems are imperfect, and we always need the pregnancy test, and the final pregnancy outcome, to tell us more about "embryo quality" than a microscope could ever reveal.

A blastocyst is an embryo which has developed to the point of having 2 different cell components and a fluid cavity. Human embryos, in culture in an IVF lab, or developing naturally in the female body, usually reach the blastocyst stage by day 5 after fertilization. Blastocyst transfer with IVF can give high pregnancy success rates with very low risk of triplets.

However, under standard IVF culture conditions, only about 25-60% of human embryos will progress to the blastocyst stage after 5 days of culture.