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Embryology 101

Medieval theories of mice originating from dirt and discarded rags aside, it had been noted since times immemorial that life begets life. Another scientific observation from the same era is that the offspring resemble their parents. We will never fully know the views of our ancestors on the problem of sex and reproduction, but throughout the millennia and across different cultures the virgin birth had always been associated with Divine Intervention. This tells us that that immaculate conception (parthenogenesis) was considered physically impossible in humans. Father might not be always known, but he must always be present. Each of us has half of our genome coming from our mother and another half from the father.

An embryologist in the IVF lab witnesses the creation of human embryos daily as a part of his/her routine job. Once the egg is fertilized by sperm, the genetics of a new human being is established. While the embryo progresses through the stages of preimplantation development, it is the embryologist's job to keep it safe and healthy. Once the embryo is transferred and implanted into mother's uterus, it is up to the mother to stay safe for the sake of her baby.

  • Day 0: Oocyte
  • Day 1: Zygote
  • Day 2: Two Cell Embryo
  • Day 3: 10 Cell Embryo
  • Day 4: Morula
  • Day 5: Blastocyst
  • Day 6: Hatching Blastocyst
  • Day 7: Hatched Blastocyst

Below are the specifics of preimplantation embryo development in human IVF: