So someone that is involved in a motor vehicle accident and becomes braindead ceases to be human and merely becomes a clump of cells and tissues from that point?
If someone is diagnosed as brain dead, then both medically and legally they are dead. We can keep their heart beating for decades, but that doesn't make the person alive.
Human life begins at conception, scientifically indisputable.
Simply not true. A single cell is not a human life.
If a parent, man or woman, decides they don't want a child 1 month into it's life citing they're "unwanted" or that raising a child might be "lengthy," would it be acceptable for that man or woman to end the child's life for their own convenience?
Obviously not, and constructing such a ridiculous strawman only weakens your argument.
The pro-choice crowd doesn't use the appropriate argument by circling around the central issue of ending human life based on convenience.
It isn't a human life, but calling pregnancy and the process of giving birth, and all the risks, complications, and implications which come with them an "inconvenience" is incredibly naive.