Assisted Hatching in IVF

Blastocyst hatching failure, due to intrinsic abnormalities in either the blastocyst or zona pellucida (ZP) of in vitro cultured embryos, may be one limiting factor in human ART efficiency. Assisted hatching (AH) involves the artificial thinning or breaching of the ZP and has been proposed to improve implantation rates in selected patients following IVF. AH procedure can be performed using various methods. These include the creation of an opening in the ZP either by drilling with acid Tyrode’s solution, mechanical partial zona dissection, or laser photoablation. The ZP can be thinned using proteolytic enzymes, acid Tyrode’s solution, or laser and totally removed by chemical and enzymatical action. AH is usually performed on day 3 after fertilization but also at the blastocyst stage. Outcome of frozen–thawed cycles can also be improved after AH. AH may be associated with specific complications, including damage to the embryo or to individual blastomeres with reduction of embryo viability and an increased risk of monozygotic twinning due to the artificial manipulation of the ZP.