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How Does an Embryo Differ From a Fetus?

David Newman
Posted Tuesday, Aug. 29, 2000, at 12:24 PM ET

A recent change in federal regulations enables government-funded researchers to experiment using embryonic tissue. How is an embryo different from a fetus?

After the 10th week of pregnancy, a human embryo is more commonly referred to as a foetus (which, incidentally, is the same thing as a fetus) to signify a new phase of development. At 10 weeks, the embryo-turned-fetus has just completed its most rapid period of cellular differentiation, a process that formed the beginnings of the most basic human structures. Roughly 4 centimeters long, the new fetus lacks working lungs and is many weeks away from being viable outside the womb. Still, with the hint of fingers, toes, and ears, it is now clearly recognizable as human.

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David Newman is a contributing editor at Legal Affairs.
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Reader Comments from The Fray:


There is no point in time when someone goes from being non-human to human, let alone the moment of conception. Becoming human is a process that occurs slowly over time; a fertilized egg is no more human than an amoeba--it is nothing more than a potential human.

And if we can clone fetuses, there is no moment of conception. Are they human by the religeous zealots' definition? It will only be a matter of time before someone implants a cloned fetus in a human womb. This will force the religious zealots into a new round of gyrations to make their religious beliefs square with scientific realities.

--Dr Atomic

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