Assisted hatching, a scientific technique used in In Vitro Fertilisation (IVF), may improve the implantation of embryos into a woman’s uterine lining by creating an opening through which the embryonic cells can hatch out. Pregnancy cannot occur unless the embryo hatches.
Just before embryo implantation, the developing embryo must “hatch” out of its outer shell (zona pellucida). Some embryos seem to have a thicker shell that may decrease their ability to hatch and therefore reduce the likelihood that they will implant. This may be due to the age of the woman or other, unknown reasons.
The unfertilised egg (oocyte) is surrounded by the zona pellucida membrane. The zona pellucida ensures that only one sperm cell enters and fertilises the egg. After fertilisation, the embryo begins to cleave into a two-cell, then a four-cell and so on. It is at this early cleavage stage that assisted hatching can be performed on embryos.
It has been shown that women aged over 37 have a tendency to produce oocytes with a harder and/or thicker zona pellucida than younger women. The same applies to women with a high level of follicle-stimulating hormone (FSH).
The problem of a harder zona pellucida is that the embryo may not hatch and thus not attach to the womb. It has been reported that up to 75% of normal embryos may never hatch. Laboratory procedures involved in IVF may add to the hardening of the zona, as the embryo is not continually exposed to the enzymes present in the natural environment of the fallopian tubes.
There is also evidence to suggest that the process of freezing and thawing embryos may cause the zona to harden, and using assisted hatching can be beneficial.
At City Fertility Centre, we offer laser-assisted hatching, which is a gentle and safe way to weaken a small section of the zona pellucida – allowing the embryo to hatch. Several studies have shown that using a laser is superior to chemical and manual hatching. Laser-assisted hatching has several advantages, including minimal handling of the embryo and delivering fast and exact control over the drilling of the hole.
Laser-assisted hatching is performed by the scientists before the embryos are transferred back to the uterus.
The potential fertility improvement that this type of treatment may yield depends on the woman’s age, diagnosis and the initial semen analysis, and should be discussed with your specialist.
Recent meta-analysis (comparison of different relevant research findings) showed that women who have undergone repeated IVF treatments without positive results can increase their chances of a pregnancy with laser-assisted hatching.
To find out more about the blastocyst embryo transfer, please read our Laser-Assisted Hatching Fact Sheet.
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