Under certain conditions (e.g., repeated failure of embryo implantation or in case of embryos with thickened zona pellucida) the effort is made to heighten the chances of pregnancy by facilitating the hatching of the embryo from the zona pellucida , which is enveloping the embryo.

Just before the embryo is transferred into the uterus, the zona pellucida is thinned with a laser. So far there is no scientific confirmation that this procedure improves the chances of success.