By learning more and more about the human genome a growing number of diseases can be detected by PGD and thus more patients can be treated. On the other hand, the early PGD (involving the egg or the embryo at the 6-8 cell stage) has been limited by low number of cells (one or two cells). This can be eliminated by taking a sample on Day 5, when it is possible to test multiple cells. In this case, however, the currently applied techniques do not make the genetic test result available on Day 5, which is the optimal time for implanting the embryo.
Recently developed vitrification methods are much more efficient in freezing the embryo, and blastocyst survival after thawing is as much as over 90%. In this way, the embryo can be implanted in a later cycle, when the genetic test results are available.
Frozen embryo