The next day after the blastocyst stage (fifth day after fertilization) the embryonic shell should hatch and embryo development should continue. However, if the embryologist detects excessive thickness of embryonic shell or if there’s a need to increase likelihood of a positive result (i.e. at least one unsuccessful embryo transfer, blastocyst needs to be vitrified, embryos used after thawing, woman is over 37 years of age), assisted hatching can be performed with a special needle, laser or chemically. This process prepares the embryo for successful binding to the uterine wall and pregnancy.
