2-Cell Stage (30 hours)

Medically reviewed by: Stephanie Curreli, MD, PhD
Last Updated: Feb 5, 2015

The two-cell stage occurs with the first cleavage of the zygote. As it reaches the 30-hour mark (that is, 30 hours after fertilization), the zygote undergoes additional divisions as it moves toward the uterus (endometrium).

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