Human life begins at conception when a new, genetically-distinct person is created, separate from both their mother and father. That new person begins to develop and, left alone, doesn't cease developing until about the age of 25. Any argument you make to terminate an unborn baby must also be acceptable when applied to a 25 year old adult. Biologically, the only real difference between the two is in arbitrary level of development.
A 2 month old baby is less developed than a 2 year old child. That doesn't negate the life of either. The same applies at any point from conception onward.
This is not a religious debate. This is a basic medical science and logic debate.
As far as the science goes, the medical consensus is that human life begins at conception/fertilization. You can go to any medical journal or textbook relating to embryology; they all say this.
The medical science has no debate; it's only in politics and society.