Assisted hatching is used when the fertilized egg is wrapped in a membrane (zona pellucida) that is abnormally thick, so much so that the zygote is unable to break the membrane and implant in the uterine wall.
# The zona pellucida is abnormally thick.
# Age (38 or older)
# Have attempted at least 3 times to have a baby using the test-tube method with healthy zygotes and have not conceived
# When the egg or the zygote is cultivated externally, the zona pellucida becomes thicker and harder. If this phenomenon is extreme, the zygote will not be able to hatch for implantation.
# Before the zygote is transferred into the uterus, a microsurgical instrument is used to break the zona pellucida and make hatching and implantation easier.
# Holes can be made with enzymes or acid, or a needle can tear the zona pellucida.