An egg fertilized (embryo) in the course of an “In vitro fertilization” (IVF) program cycle, which is sometimes augmented with an “Intracytoplasmic sperm injection” (ICSI) procedure, may require assistance to get implanted properly in the uterine lining. This is done using a special technique called “Assisted hatching”.
With this technique, the zona pellucida, the outer shell of the embryo, is either thinned or perforated. This is accomplished with acid, a micro needle, or laser.
Before Hatching / After Hatching
A Careful Laboratory Procedure
The embryo is typically allowed to reach the “8-cell” stage of development prior to treatment. This stage usually occurs on the 3rd day after a successful fertilization. During the assisted hatching laboratory procedure, the embryo is temporarily held in place with a narrow pipette and a tiny hole is made, depending on the method. The hole can be made by chemical, mechanical, or laser method.
Chemical: An extremely fine, hollow needle is used to apply a small dose of a mildly corrosive agent to the embryo’s zona pellucida. A hole appears due to the acidic reaction and then the embryo is washed to cleanse it of the acidic solution.
Mechanical: A solid needle with a microscopically fine point is used to mechanically drill and remove a limited amount of material from the embryo’s zona pellucida, leaving behind a small hole on its surface.
Laser: A precisely measured beam of coherent light is used to instantaneously (almost) burn a small hole on a selected portion of the embryo’s zona pellucida. This method, called laser-assisted hatching, is very common.
After making hole on the embryo’s outer shell, the embryo is briefly returned to the incubator and in a short while the embryo transfer process is started.
Prevalence of Assisted Hatching
The adoption of this practice varies among fertility clinics. Some clinics choose to exercise the technique with all patients, but others restrict its use to specific cases:
With patients experiencing significant difficulties in achieving a pregnancy after repeated IVF failures.
- With patients whose “follicle stimulating hormone” (FSH) levels are elevated at a critical point (Day 3) during their natural menstrual cycles.
- With patients over the age of 37 electing to attempt a pregnancy with their own eggs.
- With embryos suffering from slow cell division or excessive fragmentation.
- With embryos exhibiting unusually thick outer shells.
Assisted Hatching Advantages
Assisted hatching offers improvements over standard IVF treatments. With assisted hatching there is an increase in rate of embryo implantation and pregnancy. Some advantages are:
- Only less number of embryos are required for transfer.
- Embryos have a better chance of developing to their blastocyst stages before implantation, which is preferred by some clinics.
Assisted Hatching Disadvantages
However, assisted hatching does have a few drawbacks:
- Making a hole on the protective outer shell of the embryo may put it at increased risk of infection.
- Nearly 1 percent of all treated embryos may be damaged or destroyed.
- The occurrence of identical twins may increase slightly.
Success rates do vary among fertility clinics. The various methods employed for assisted hatching may show differing results. The best outcomes will be obtained by skilled embryologists operating with well-equipped laboratories staffed by experienced personnel. A patient interested in this technique should consult a fertility professional for a fuller discussion.