Assisted Hatching

Ova and embryos are surrounded with an elastic envelope, the so called zona pellucida. For a correct implantation in the womb, an embryo in the blastocyst stage has to hatch out of this cover.

Under certain circumstances the zona pellucida can be hardened and hereby a hatching of the embryo can be complicated or impossible. This can be the case, for example, with embryos which emerged from cryopreserved ova. Also the age of a woman seems to play a role with the hardness of the zona pellucida.