Assisted Hatching

Assisted hatching at a glance

  • Assisted hatching is a technique that helps an embryo break free from its outer shell so it can implant in the uterus for a pregnancy.
  • The procedure uses a laser to artificially rupture the embryo’s zona pellucida (outer shell) during in vitro fertilization (IVF).
  • According to the American Society for Reproductive Medicine (ASRM), assisted hatching can slightly improve chances of embryo implantation in women with poor prognosis and previous failed IVF attempts.
  • Use of assisted hatching is not routinely recommended, and the procedure is debated within the medical community due to potential complications and little proof of increased live-birth rates.

What is assisted hatching?

Assisted hatching involves the artificial breaching of the zona pellucida, or the embryo’s outer shell, as a technique to improve implantation and pregnancy rates following IVF. Since the early 1990s, many assisted reproductive technology programs have incorporated the use of assisted hatching in an effort to improve clinical outcomes.

In order for a pregnancy to occur, a fertilized egg (embryo) must travel from the fallopian tube and implant in the uterus. Before it can implant, an embryo must hatch by breaking through a protein capsule that makes up its outer shell, called the zona pullucida.

Failure to hatch can be due excessive thickness the zona pellucida.

Assisted hatching is typically performed on day three after fertilization. On the day of the embryo transfer, an embryologist carefully evaluates embryos for quality. Depending on their stage of development, an embryologist assists the hatching by making a small nick in the zona pellucida using a laser.

Lab specialists then rinse and incubate the embryos for a few more hours before the embryo transfer to the uterus. This procedure may occasionally increase the chance that an embryo will implant in the uterine wall and facilitate a successful pregnancy.

Fertility specialists do not recommend routine use of assisted hatching. But breaching the zona pellucida with a laser for the purpose of embryo biopsy and preimplantation genetic testing is now a standard of care and is considered very low risk when performed by a trained and experienced embryologist.

Who should seek assisted hatching?

Often IVF failure is due to an embryo’s failure to implant in the uterus. Assisted hatching can improve the chances of implantation during IVF and is considered an option for patients who are able to achieve good fertilization and embryo cell development, but the zona pellucida is excessively thick and they do not conceive.

Assisted hatching slightly improves clinical pregnancy rates, particularly in poor-prognosis patients. Assisted hatching is sometimes recommended for patients with the following:

  • Embryos with thick or irregular zona pellucida, which may restrict the embryo from hatching or “breaking out” in order to attach to the uterine lining.
  • Diminished ovarian reserve, a condition determined before fertility treatments begin in which a woman’s ovary has fewer embryos than normal and the chances of achieving a pregnancy are low.
  • Have experienced previous implantation failures and whose chances of achieving pregnancy may be increased with the help of assisted hatching.

Assisted hatching considerations

Some complications can occur during assisted hatching independent of the IVF treatment itself. There is a small risk the embryo may be damaged by the actual hatching procedure. Some embryos and embryonic cells may also become damaged during the micromanipulation process, which can lead to IVF failure but will not increase the risk of birth defects. In addition, assisted hatching has been associated with a very slightly increased risk of monozygotic (MZ) twin pregnancies, or identical twins.