Assisted Hatching IVF

 

In vitro fertilization (IVF) failure is a frustrating experience for individuals and couples, and it is often caused by an embryo’s failure to implant in the uterus.

For women who have failed IVF or have a poor prognosis for IVF, thefertility doctor may recommend a technique known as assisted hatching.

What Is Assisted Hatching?

After an egg is fertilized in the laboratory, the cells begin to divide. During these initial stages of development, the embryo is contained in a layer of proteins known as the zona pellicuda. In order to successfully implant into the uterine lining, an embryo has to hatch out of the zona pellucida and attach to the walls of the uterus.

Assisted hatching is a newer lab technique that was developed when fertility experts observed that embryos with a thin zona pellucida had a higher rate of implantation during IVF. With assisted hatching, an embryologist uses micromanipulation under a microscope to create a small hole in the zona pellucida. This happens on the fourth day of embryo development when the embryos contain an average of six to eight cells.

The embryos are stabilized by a holding pipette, and on the opposite side a small pipette containing an acidified solution creates a small defect in the zona pellucida. The embryos are then rinsed to remove any excess acid solution and returned to the incubator for a few hours before transfer into the uterus.

Who should be treated with assisted hatching?

The most commonly used indications for assisted hatching with an in vitro fertilization case are:

  • Age factor – the female partner is older than 37
  • Egg quantity and quality factor – cases in which the woman’s day 3 follicle stimulating hormone (FSH) level is elevated, or with a low AMH level or low antral follicle count
  • Embryo quality factor – cases with poor quality embryos (excessive fragmentation or slow rates of cell division)
  • Zona factor – cases with embryos that have a thick outer shell (zona pellucida)
  • Previous IVF failure – cases that have had one or more previous failed IVF cycles

In our IVF clinic, we use assisted hatching for day 3 embryo transfers on just about all cases – because we think it increases the pregnancy and delivery rates.

How is assisted hatching performed using acid Tyrode’s solution?

  1. The embryo is held with a specialized holding pipette.
  2. A very delicate, hollow needle is used to expel the acidic solution against the outer “shell” (zona pellucida) of the embryo.
  3. A small hole is made in the shell by digesting it with the acidic solution.
  4. The embryo is then washed and put back in culture in the incubator.
  5. The embryo transfer procedure is done shortly after the hatching procedure.
  6. Embryo transfer places the embryos in the uterus where they will hopefully implant and develop to result in a birth.

 

Assisted hatching does not increase live birth rates

Pregnancy rates for in vitro fertilization procedures with assisted hatching have been shown in some published studies to be higher than for IVF without hatching. There is an improvement in the rate of embryo implantation and pregnancy in our IVF clinic with the use of assisted hatching. Apparently, this benefit is not seen in all IVF programs.

It is possible to damage embryos with hatching and lower the pregnancy rates. Therefore, it is essential that if assisted hatching is done, it must be expertly performed by properly trained embryologists.

The actual pregnancy and live birth rates seen in an individual IVF center will vary according to the hatching technique used, the overall quality of the laboratory, the skill of the individual performing the hatching, the embryo transfer skills of the physician, and other factors.

Other factors predicting assisted hatching success are patient characteristics. Those that benefit most from assisted hatching include women over 38 and women who have attempted IVF several times without success. However, even in these groups, live birth rates were not improved in women that used assisted hatching. Therefore, the ASRM does not promote the routine use of assisted hatching during IVF.

Why the controversy?
At a quick glance, assisted hatching appears to be beneficial. Still, complications can and do occur. For instance, some embryos and embryonic cells become damaged or destroyed during the micromanipulation technique. This can lead to IVF failure.

While some research studies have shown that assisted hatching has increased pregnancy and implantation rates for patients, the procedure does not appear to boost live-birth success rates after IVF. Therefore, fertility specialists may consider the ASRM recommendations and not use assisted hatching routinely during IVF.