Assisted Hatching

After an egg is fertilized by sperm, it becomes an embryo. Before the embryo can attach to the wall of the uterus, it must emerge from the outer layer (zona pellucida), which is also called ‘hatching.’ Assisted hatching involves thinning the outer layer, or making a home in it some way.


What is the zona pellucida?

The shell around the embryo is called the zona pellucida. This non-cellular layer surrounds an egg, as well as an embryo (until day six of development). After day six, the embryo hatches (breaks free) from the zona pellucida. This hatching process allows the embryo to implant and attach to the uterine lining.


How is assisted hatching done?

Assisted hatching occurs when the embryo is in the laboratory. After in vitro fertilization (IVF), embryos are kept in a special dish. Before being transferred back to the woman’s uterus, a hole is made in the outer layer.


What are the steps of the assisted hatching method?

Assisted hatching involves:

  • Step one – On day three of the embryo development, an embryologist thins or makes a hole in the outer layer surrounding the embryo. This is done using a weak acid and tiny glass pipette or by using a microlaser or microtool.
  • Step two – When acid is used, the embryo is washed with a special solution after the procedure.
  • Step three – To prevent infection, the woman must be given antibiotics.


Does assisted hatching increase my chances of having a baby?

Fertility specialists and reproductive health experts believe using assisted hatching results in higher pregnancy rates for some couples. Many older women have thicker zona pellucida around the resulting embryos. Making a weak point in this outer later assists with implantation. Rates for live births are:

  • 37% for women age 34 years and under
  • 26% for women ages 35 to 37
  • 21% for women ages 38 and 39
  • 14% for women ages 40 to 42
  • 6% and less for women ages 43 and older


What risks are associated with assisted hatching?

Current research shows that assisted hatching does not cause any abnormalities to the baby. The rate of birth defects with IVF/assisted hatching is the same as with normal conception. Since the outer layer around the embryo is manipulated, the embryo remains unharmed. However, when more than one embryo is transferred, there is a chance of multiple births.


What methods are used to thin the zona pellucida?

To create an opening or thin the zona pellucida, the embryo must be treated by:

  • Laser drilling – A special laser is used to thin the outer layer.
  • Tyrode’s solution – This mild acid contains a proteolytic enzyme to dissolve the zona pellucida.
  • Partial zona dissection (PZD) – A micro-needle is used to pierce a small opening in the outer layer.
  • Piezo-micromanipulator – To create a tiny opening in the zona pellucida, this device uses electric vibrations.
  • Mechanical expansion – To stretch the outer layer, a special instrument is used.


Who is a candidate for assisted hatching?

Assisted hatching has benefited thousands of infertile couples around the world. Candidates include:

  • Women with elevated follicle stimulating hormone (FSH) levels.
  • Any woman age 38 years and older.
  • Women with poor embryo quality.
  • Anyone with poor egg quality.
  • Couples who have failed to conceive in prior in vitro fertilization cycles.