Hatching Blastocyst

Definition - What does Hatching Blastocyst mean?

A hatching blastocyst is a developing embryo (at around five days after fertilization) that is hatching out of its protective coating, known as the zona pellucida.

A hatching blastocyst may also be know as a hatched blastocyst or a zona-free blastocyst when the process of hatching is complete.

FertilitySmarts explains Hatching Blastocyst

There is a protective covering around an egg called the zona pellucida. This coating plays a role in fertilization, helps to contain cells in very early development, and allows a fertilized egg to successfully migrate through the fallopian tubes and into the uterus.

As the fertilized egg divides and develops, it becomes a blastocyst. One of the distinct features of a blastocyst is its fluid-filled cavity. This fluid plays a critical roll in helping the blastocyst the "hatch" from this protective coating through a series of expansion and contraction. The removal of the zona pellucida is a critical step that is necessary in order for the blastocyst to adhere and eventually implant within the uterine lining.

A small study found that during in vitro fertilization (IVF), transferring spontaneously hatching or hatched blastocysts resulted in higher implantation and pregnancy rates than when using expanded blastocysts that had not yet hatched.

A procedure called assisted hatching may be an option during IVF treatment to help the blastocyst hatch from the protective shell.

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