Generally the following:

-          Normal fertilization

-          The rate at which they develop

-          Where they are from a development point of view on either day3 or 5 ( Cell number or morphology depending whether day 3 or 5)

-          The percentage of fragmentation within the embryo

-     The thickness of the Zonb Pellucida (“shell”)

- Week 32 answers kindly provided by Dr. Stephan Volschenk -

Fortunately the “American” era of “embryo glue “has come and gone quickly. We understand today  that whether an embryo will implant or not is based on three factors:

1)       The quality of the endometrium.

2)       The technique and experience of the person doing the embryo transfer.

3)       The quality of the embryo, which is dependent on the quality of the sperm and the quality of the egg.

It is therefore clear then that no amount of “glue” of what ever substance is going to ensure that the embryo implants and lead to a pregnancy.

- Week 31 answers kindly provided by Dr. Stephan Volschenk -

-1dpt ..embryo is growing and developing
0dpt… Embryo is now a blastocyst
1dpt….Blastocyst hatches out of shell on this day
2dpt.. Blastocyst attaches to a site on the uterine lining
3dpt.. Implantation begins,as the blastocyst begins to bury in the lining
4dpt.. Implantation process continues and morula buries deeper in the lining
5dpt.. Morula is completely inmplanted in the lining and has placenta cells & fetal cells
6dpt…Placenta cells begin to secret HCG in the blood
7dpt…More HCG is produced as fetus develops
8dpt…More HCG is produced as fetus develops
9dpt…HCG levels are now high enough to be immediately detected on HPT

* This excerpt from an unknown source was confirmed to be reasonably correct by Dr.V

- Week 17 answers kindly provided by Dr. Stephan Volschenk -

- Week 14 answers kindly provided by Dr. Stephan Volschenk -

Added 24 October 2008: See also - http://www.nashvillefertility.com/embryo_development_photo_gallery.htm

Anything below 20% fragmentation.

- Week 11 answers kindly provided by Dr. Stephan Volschenk -

The biggest factor playing a role during implantation is the quality of the embryo – about 75-80%. The rest is made up of uterine factors, such as the presence of submucosal and large intramural fibroids, adenomyosis etc. and immunological and thrombotic factors such as HLA incompatibility, thrombophylia’s, etc.

- Week 6 answers kindly provided by Dr. Stephan Volschenk -

Embryos fragment mainly due to two reasons:
1) Poor oocyte or poor sperm quality leading to an embryo of poor quality.
2) Some embryos do not handle the stress of being in the incubator and being evaluated on a daily basis too well, and if of borderline quality therefore fragments.

- Week 3 answers kindly provided by Dr. Stephan Volschenk -

The transport of the embryos is possible, as long as the recipient lab uses the same protocol to thaw the embryos as was used to freeze them. This can usually be solved with inter laboratory communication.

- Week 2 answers kindly provided by Dr. Stephan Volschenk -