In the process of the reproduction of any living being there is no beginning of life in general, because there is no period of non-life in the entire sequence of events from mating to birth. The mother and father are alive. So are the individual sperm and egg. The zygote formed from their union is alive, as is the developing fetus during its entire term. Finally, the child delivered at birth is alive.
From beginning to end there is an unbroken continuum of life. Life doesn't begin at some stage of development; the unborn is alive at every stage. The fact that the fetus is growing biologically proves that it's alive, and biological growth is evident immediately upon conception.
Stand firm in Christ,
Koukl, Greg. Precious Unborn Human Persons. Page 11.