Investigators aim to investigate the effect of elimination of blastocoelic fluid by creating a large hole in the zona pellucida at the cellular junction of the trophectoderm cells located far away from the inner cell mass with a laser pulse before vitrification.

Human blastocyst formation begins about 5 days after injecting a single sperm into an oocyte in ICSI cycle or incubation of them in IVF cycle. Human blastocyst consists of cells forming an outer layer called trophotoderm that will form the placenta in case of successful implantation, an inner cell mass which become the fetus, a fluid-filled blastocoel cavity in the center, and a surrounding zone pellucida from which the embryo hatches to implant in the uterus. Human blastocyst contains a large amount of liquid in the blastocoel, which alters the infiltration of vitrification solution during the vitrification procedures leading to ice crystal formation. Therefore, investigators need to compare blastocyst survival, clinical pregnancy and implantation rates between vitrified untreated expanded blastocysts and vitrified blastocysts with artificially eliminated blastocoels by a laser pulse prior to vitrification

Inclusion Criteria:

• BMI of ≤ 32

Exclusion Criteria:

• Non-expanded blastocysts.
• Women who had uterine pathology or abnormality.