Life Begins

and the two will become one flesh. So they are no longer two, but one.
Mark 10:6

"The membrane of one of them fuses with that of the egg. This sperm stops all swimming movements immediately, and a change takes place in the egg membrane which effectively stops any other sperm from fusing with it. Enzymes are released from the egg's surface which alter the structure of the zona and prevent any further sperm from penetrating it. These events take place within a few minutes of fusion, and the chromosomes of the successful sperm begin to move into the egg cytoplasm. The final part of fertilization, taking longer but absolutely vital, is the egg's resumption of meiosis to get rid of the extra set of chromosomes. Two to three hours after fusion the second polar body is extruded, and the fertilized egg is left with one set of maternal chromosomes to complement the paternal set from the sperm. Although the two chromosome sets are independent to begin with, and so are called pronuclei (these can be seen in Figure 14), by the time of the first division of the fertilized egg the chromosomes have mingled and will all come to lie in the same equatorial plane. This would appear to mark the time at which the embryo becomes autonomous, but as you will see below, this is not necessarily the case. However, it is certainly a prerequisite for a new individual."
http://openlearn.open.ac.uk/mod/resource/view.php?id=193044

Life is never interrupted in the process of procreation. A new living human is formed from the physical uniting of the chemical materials in sperm and egg cells onlly under the condition of them being "alive". Both sperm and egg must be living cells to complete the process. The life resident in each of the two components combines together to become a singular force that animates the new single cell human at the time the sperm and egg fuse.

Still other seed fell on good soil, where it produced a crop--a hundred, sixty or thirty times what was sown.
Matthew 13:8

Ensoulment is the immediate combination of the two life forces that animate the two reproductive cells, into one unique human life force animating one unique human cell. A new distinct human being comes into existence at that moment.

Flesh gives birth to flesh, but the Spirit gives birth to spirit.
John 3:6

Rights are inherent with being. Human rights are inherent to being human. Human rights are not bestowed by anyone. They are inalienable to each and every human creature. Primary among those rights is the right to life. The very fact of being a conceived human being is what bestows full human rights upon each human being.

You are a child of the universe - You have a right to be here.
(Desiderata)

To think that any other human, or group of humans, can arbitrarily decide that the life of any other human being is without the right to life, and that that life can discarded, or taken by another based on any arbitrary criteria such as age, health, dependency, race, utility ... is nothing but unconscionable madness for anyone anywhere. It is always the strong over the weak, and is the single most disgusting and blatant manifestation of pure evil today.

"Don't be sidetracked by pro-abortion comments that typically come up. The most common is to dismiss the undeniable facts..."
http://www.catholicnewsagency.com/resource.php?n=884