Assisted hatching overview
- Assisted hatching involves the artificial thinning or opening of the zona pellucida, the non cellular protective layer surrounding the unfertilized egg and the embryo prior to implantation.
- Hatching is a necessary step before the embryo can attach to and implant in the lining of the uterus, resulting in pregnancy.
- Failure to hatch, due to basic irregularities in either the zona pellucida or the embryo, may be one of the factors limiting the efficiency of reproduction and affecting fertility.
- Assisted hatching increases the chances of the embryo successfully implanting and is frequently a part of in vitro fertilization (IVF).
What is assisted hatching?
Assisted hatching is a procedure performed in the IVF lab on the zona pellucida around the developing embryo to increase the chances of implantation. Assisted hatching is generally performed on day 3, 5 or 6 after fertilization using various methods. Chemical hatching has largely been replaced by precision laser methods.
After the egg is fertilized it becomes an embryo, dividing into many more cells to form a blastocyst after about five or six days. The blastocyst is a multi-cell embryo with a cavity of fluid. The embryo is protected by a layer of thick protein called the zona pellucida.
As the blastocyst prepares for implantation, the cavity becomes larger and the zona pellucida thins, making it easier for blastocyst enzymes to create an opening for the embryo to get out, or hatch, from the zona pellucida. If the blastocyst fails to hatch, it cannot attach to or implant in the uterine lining.
In order to boost the odds of success, some embryos may benefit from assisted hatching. This procedure helps the embryo to break out of the zona pellucida and attach to the uterine wall.
When is assisted hatching recommended?
Assisted hatching increases the chances of implantation during IVF. Women who may consider assisted hatching include:
- Those who have embryos with a thick or irregular zona pellucida
- Women with diminished ovarian reserve
- Women with poor quality embryos as evaluated by the IVF lab
- Women undergoing frozen embryo transfer cycles
- Women who have experienced previous implantation failures
What are the risks of assisted hatching?
If performed improperly, assisted hatching could harm the embryo by damaging some of its cells.
Additionally, a few studies have suggested that assisted hatching correlates with monozygotic (identical) twins. However, a correlation does not mean that assisted hatching causes identical twins.