Before an embryo implants into the uterine wall to establish a pregnancy, it needs to shed its outer shell. This shell is called the zona pellucida. The process in which the zona pellucida is shed is called hatching. Failure of the embryo to hatch may be one of the many factors that cause failure of implantation.
Assisted hatching is a procedure in which the zona pellucida of an embryo is partially opened to help facilitate implantation and pregnancy. Assisted hatching is performed by one of our embryologists immediately before embryo transfer or on day 3 for those embryos that will eventually undergo preimplantation genetic screening as blastocysts. With the assistance of a powerful microscope the embryologists can visualize the embryo shell and with laser open a small hole in the shell without harming the embryo. This opening in the shell allows the embryo to more easily emerge or “hatch” out of the shell in order for it to implant in the wall of the uterus.
At many IVF clinics, assisted hatching was once used universally for all IVF patients. However, multiple studies have been published that show that it can only improve pregnancy rates in certain populations of patients, including women 38 years and older, women with two or more failed IVF cycles or women with a poor prognosis. Hatching is also currently used in all frozen embryos.