Assisted Hatching in Frozen Blastocysts

Inclusion Criteria: * In-vitro fertilization patients at the investigators' institution, intended to undergo a transfer of a frozen five-day embryo (blastocyte) * 18 to 39 years old * First to third treatment cycle * Patient has previously had a maximum of four embryos transferred. Exclusion Criteria: * Over 40 years old * Congenital or acquired uterine malformations * Hydrosalpinx * Chronic autoimmune diseases * Embryo intended to be undergo preimplantation genetic diagnosis