Summations Only

The Justices did not make a decision about when life began.
Their decision was based on foetal viability and the extent of the states power to intervene.From Wiki

quote:

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The Court asserted that that the government had two competing interests — protecting the mother's health and protecting the "potentiality of human life". Following its earlier logic, the Court stated that during the first trimester, when the procedure is more safe than childbirth, the decision to abort must be left to the mother and her physician. The State has the right to intervene prior to fetal viability only to protect the health of the mother, and may regulate the procedure after viability so long as there is always an exception for preserving maternal health. The Court additionally added that the primary right being preserved in the Roe decision was that of the physician's right to practice medicine freely absent a compelling state interest — not women's rights in general. The Court explicitly rejected a fetal "right to life" argument.

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There is little point using a definition of life as a counter-argument for the Roe vs Wade decision.
They didn't claim that a foetus was not alive.Edited by Panda, : No reason given.Edited by Panda, : No reason given.Edited by Panda, : No reason given.

The cell at the top is the brain (or is it the head?).
The cells at the sides are the arms and those at the bottom are the legs.Draw a smiley face on the top cell and you will instantly see it is an actual child!