Morula

Definition - What does Morula mean?

The morula is a stage of post-fertilization development, when a fertilized egg known as a zygote transitions to a mass composed of around 10-30 cells.

During in vitro fertilization (IVF), morula phase typically occurs on day 4 of development. The morula phase is the final phase prior to blastocyst development.

FertilitySmarts explains Morula

The primary indication of the morula phase is the presence of many cells with semi-undefined borders that are beginning to melt together. As the embryo compacts, the individual cell walls become fuzzy, creating the presence of a mass that resembles a berry.

The morula phase is the earliest period during assisted reproductive technologies (ART) that preimplantation genetic screen (PGS) or diagnostic testing is possible. This is done by removing individual cells known as blastomeres.

Major stages of development from conception to birth include:

  • Zygote, a fertilized egg that forms when sperm and egg combine
  • Morula, forms around day four
  • Blastocyst, forms around day five
  • Embryo, starts the third week after conception or fifth week of pregnacy
  • Fetus, nine weeks after conception or 11th week of pregnacy
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