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Anuradha Housnur: Cleavage vs. Blastocyst: What’s the Difference?

Anuradha Housnur/LinkedIn

Jul 4, 2026, 14:48

Anuradha Housnur: Cleavage vs. Blastocyst: What’s the Difference?

Anuradha Housnur, Head-Training In Clinical Embryology, Chief Embryologist at Seeds of Innocens IVF and Fertility Centres, shared a post on LinkedIn:

“Cleavage vs. Blastocyst: What’s the Difference?

Not all embryos are at the same stage of development and understanding these stages is fundamental in embryology.

Cleavage Stage (Day 2–3)

The embryo undergoes rapid mitotic divisions without increasing in size, resulting in 2–8 blastomeres enclosed within the zona pellucida. At this stage, embryologists evaluate:

Cell number
Blastomere symmetry
Degree of fragmentation
Presence of multinucleation

Blastocyst Stage (Day 5–6)

As development progresses, the embryo forms a fluid-filled cavity (blastocoel) and differentiates into:

Inner Cell Mass (ICM): Gives rise to the fetus.
Trophectoderm (TE): Develops into the placenta and supporting tissues.

At this stage, embryologists assess:

Degree of blastocyst expansion
ICM quality
Trophectoderm quality

Why does this matter?
Blastocyst culture allows better assessment of developmental competence and embryo selection. However, not every viable embryo reaches the blastocyst stage in vitro, and both cleavage-stage and blastocyst-stage embryo transfers have their place depending on the clinical scenario.

At Seeds of Innocens Fertility Academy, our students learn to identify, evaluate, and grade embryos at every developmental stage through comprehensive theory and hands-on laboratory training building the expertise required for a successful career in clinical embryology.”

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