Blastocyst transfer

Blastocysts are embryos in between the 64- to 128-cell stage. Embryos reach this stage in about 5 days after follicle puncture given ideal conditions.

The blastocyst has a high chance of implantation (about 35%) and therefore leading to a pregnancy. Because of the shortened time frame between embryo transfer and the embryo implantation in the uterus, there has been a decrease in tubal pregnancies thanks to blastocyst transfer. These are the reasons why it is preferred to cultivate embryos until blastocyst state in many countries.


This product is a natural substance called hyaluronic acid, which is added to the culture medium before embryo transfer and has the brand name “embryo glue” or UTM. It is supposed to increase the embryo’s ability to adhere to the uterine wall but does not influence the embryos development.

Assisted hatching

Embryos and egg cells are covered by a coating similar to connective tissue, the zona pellucida. To implant, embryos at the blastocyst stage usually hatch from the zona pellucida.

Under certain circumstances the zona pellucida can be hardened and make hatching difficult or impossible. For example, this may be the case for embryos that developed out of cryopreserved egg cells. The woman’s age seems to affect the hardness of the zona pellucida as well.

It is possible to ease hatching by using a laser to melt a small hole in the zona pellucida. This procedure does not impair the development of the embryo.

Oocyte with opened zona pellucida


If, during an IVF or ICSI treatment, more egg cells are fertilized than are intended for transfer, spares can be cryopreserved and used for additional attempts.

The fertilized egg cells can be stored indefinitely in liquid nitrogen since all biological processes are halted at such low temperatures. The egg cells do therefore not age.

Cryopreservation makes it possible to efficiently use the fertilized egg cells during thawing cycles, without further follicle punctures or stimulation of the ovaries. That also makes this therapy option less taxing on the body.

Cryopreservation of fertilised oocytes

Storing of the fertilised oocytes


Besides the fertilization success, additional attributes of the spermatozoon, which are usually not visible under the microscope, are important for the further development of the embryo. These mostly entail damage to the DNA. With a special test, sperm with intact DNA can be identified and selected for ICSI. The so called PICSI method binds the suitable sperm to a special hyaluronic acid coating and isolates them that way.

Polar body diagnostics

A high percentage of early human embryos exhibit a misdistribution of individual chromosomes. This is why a lot of them are not able to develop and do not lead to a pregnancy or result in an abortion. Since an amniocentesis is only possible in an advanced pregnancy, an examination of the embryo before the transfer would offer a great advantage for the IVF. Unfortunately this is not possible in Germany due to the embryo protection law. Instead, there is another method which does not offer information about the embryo but can examine the distribution of chromosomes in the egg cell. Studies have shown that about 90% of all chromosome misdistributions have their origin in the egg cell.

During this procedure the polar bodies, a no longer required part of the egg cell, are extracted via a small glass capillary and are then examined by a human geneticist. The polar bodies develop during meiotic cell division and reflect the chromosome content of the egg cell. Should their number differ, a misdistribution of chromosomes in the egg cell is likely.

An indication for polar boy diagnostics exists

  • for patients older than 35 years
  • after multiple implantation failures of transferred embryos
  • after multiple previous abortion
  • in case of noticeable findings in a clinical report, for example translocations.