"Based upon clinical studies" is really a more valid thing to say than "the science says". Though without further information it's just as vacuous.

Cells are of course alive, but a cell is never going to develop into a human being. That requires a fertilised ovum. There's nothing in anyway controversial about saying that a life provisionally starts at conception. Where differences can arise is about the stage of development at which it should be regarded as entitled to continue developing. That's a matter of culture and politics rather than science. (Religious views being one aspect of the culture.)