New findings regarding the physiology of embryos have resulted in the development of better culture mediums. This allows the cultivation of embryos to reach a blastocyst stage.

These new mediums minimise the risk of losing the embryo’s viability and allow the embryos to be kept in culture until the 5^th day (blastocyst stage) which is the preferred method.

• The fertilized embryo usually takes 5 days to reach the uterus (in case of implanted embryos on the 2^nd or 3^rd day after the follicle puncture, these arrive at least 2 days earlier in the uterus cavity).
  
  
• While waiting for the blastocyst stage, only embryos that present an ideal development potential can be used for the transfer.
  
  
• We can identify those embryos that remain in the 4 to 8 cell stage (this would not be possible using conventional culture medium). This ability to identify abnormal embryos means using a blastocyst culture is recommended for women over 38 years of age.
  
  
• The risk of chromosome abnormalities increases with the woman’s age and abnormal embryos tend not to develop in the first few days.
  
  
• In the KinderWunschKlinik we implant a maximum of two blastocysts in the uterus. This reduces the risk of triplets. The pregnancy rate from blastocyst transfers is of approx. 62% per attempt.
  
  
• The tubal pregnancy rate is also manifestly reduced through the use of blastocysts due to the fact that, on the 5^th day after the follicle puncture, the risk of a move back into the fallopian tubes is minimised.
  
  
• The ejection of implanted embryos is avoided due to the diminished movement of the uterus. This is the big advantage of the transfer taking place on the 5^th day.
  
  
• Due to legal regulations, the blastocyst technique is not practicable in Germany, Italy or Switzerland. However in Austria it leads to excellent pregnancy rates as all oocytes won can be fertilized and cultivated until blastocyst stage!