Release of Zona Pellucida.


Prior to implantation, lytic factors in the endometrial cavity are essential in degenerating the zona pellucida that surrounds the blastocyst, otherwise known as “hatching”.

The theory is that a molecule secreted from the blastocyst activates a lytic precursor, most likely plasminogen and is responsible for the degradation of the zona pellucida membrane. This is hypothesised as placing an unfertilised egg within the uterus under same conditions does not elicit this hatching.

Sometimes the zona pellucida is toughed and can therefore cause fertility problems, as implantation cannot occur when the zona pellucida is still intact. The procedure known as 'assisted zona hatching' (AZH) is performed, which involves a small hole made by micromanipulation to the zona pellucida to facilitate this hatching (see link).


Assisted hatching image: www.ivf.com/ivf_hatching.html 

Fast Facts

Assisted hatching is performed in conjuction with IVF treatment in women that have failed IVF cycles, poor embryo development, are 38 years old plus or have thickened embryo shells.  Studies show that it greatly increases the implantation rates and pregnancy in these couples.

Fast Facts

Zona pellucida glycoproteins (ZP1, ZP2 and ZP3) are involved in immunocontraception.  This is a birth control method using the zona pellucida of one animal species and injecting it into the bloodstream of a second species, resulting in sterility of that animal due to the rejection of pregnancy by the immune system.  Commonly used in wildlife to control population sizes.