This procedure is usually recommended after there have been repeated and unexplained IVF failures or for patients with a poor prognosis.
The fertilization takes place in the lab during IVF treatment. But a fertilized embryo does not usually guarantee a pregnancy.
The transferred embryo has to implant itself into the endometrium & “stick” for pregnancy to occur.
The implantation rate or the percentage of embryo transfers that “stick” is almost 50% in women under 37 years of age but women older than this, however, it’s less than 10%.
Among the several theories on this failure, one theory is that the embryo doesn’t hatch properly.
The lack of hatching may occur because the embryo has an unusually hard shell, or because something in the lab environment has artificially interrupted the hatching process.
Assisted Hatching aims at overcoming the hurdles that are preventing hatching, improving the odds of implantation success and ultimately leading to a pregnancy.
The embryo created using IVF, is surrounded by a hard outer layer of cells or a shell called the zona pellucida.
Once a single sperm cell enters the shell and fertilizes the egg, the zona pellucida hardens. This hardening helps to prevent more sperm cells from entering the now-fertilized zygote.
As the zygote travels down the fallopian tube and develops into the blastocyst stage, the zona pellucida expands & begins deteriorating.
Around day four of its development, the shell cracks open and the embryo emerges, leaving behind the thin protein shell. This stage is identified as the embryo hatching process.
An embryo needs to break free of this “shell” to implant into the uterus further developing into a pregnancy.
A procedure where the embryo is helped to “hatch” from its “shell” by creating a small crack in the zona pellucida, is known as Assisted Hatching. It helps an embryo implant in the uterus, leading to higher pregnancy rates in some patients.
This procedure is generally performed on the third day of embryo development, where embryologists use a laser to create a very small hole in the zona pellucida. It can also be performed on previously frozen and thawed embryos.
A laboratory procedure, Assisted Hatching is occasionally done along with in vitro fertilization (IVF) treatment. IVF consists of mixing the eggs with sperm in a laboratory.
When a sperm succeeds in penetrating the egg, it is considered a fertiliser. The fertilized eggs are observed for 3 to 6 days as they divide & develop into embryos.
The best embryo is then placed into the woman’s uterus in the hopes of her getting pregnant. As the embryo develops, a protective shell (zona pellucida) surrounds it.
The embryo generally breaks out of the shell as it grows. But in some cases, an embryologist uses micromanipulation under a microscope to create a small hole in the zona pellucida.
This is performed on the third day of embryo development when the embryos contain an average of six to eight cells. This process is called assisted hatching.
This is performed in the hope that the assisted hatching might help the embryo expand, implant into the uterine wall, & finally lead to a pregnancy.
Ideal Candidates for Assisted Hatching
Not recommended for all patients, assisted hatching may be helpful in women who are older than 37 years or who have had a prior history of IVF failure.
Assisted hatching is a modern lab technique developed when fertility experts noticed that embryos with a thinner zona pellucida had a higher rate of implantation during IVF.
Assisted hatching can increase the pregnancy & delivery rates and is significantly helpful for couples with a poor prognosis whose embryos lack sufficient energy to complete the hatching process.
However, assisted hatching is a difficult technique and it is possible to damage embryos with hatching and lower the pregnancy rates.
Thus the success is largely dependent on the embryologist’s experience and technique. Always talk with your fertility clinic about how successful they have been with the procedure in the past.
Dr Shivani Bhutani has been successfully using the technique with a high success rate and has significant experience in the procedure.