Those with conscientious objections to induced abortion consider a fertilized egg cell as the very earliest stage of human life. But however abstract it may seem, aborting at this early stage is a form of murder. God's commandments are as clear as crystal as far as the basic ethics are concerned: the sixth commandment of the Ten Commandments says 'Thou shalt not kill". The discussion does not usually focus so much on the validity of this commandment, as on the question as to when an unborn child can be considered to possess life.
If one assumes that there is human life when the outside of an embryo can be clearly distinguished from that of a mammal (for instance a monkey), then human life only exists from the eighth week of pregnancy. If the entire development of the central nervous system is taken as the standard, then human life begins (a lot) later. There is also a school of thought that defines the first breath as being life. Clearly these different points of view can play a part in deciding the gestational age within which many consider that an induced abortion may be performed (so with impunity). And strictly interpreted, with impunity implies: guiltless.
The Bible gives good grounds for the argument that there is life at an early stage. Psalm 139 in particular speaks very tenderly on this matter. Not only does it concern one of the most distinguishing aspects between man and beast, but also the 'completeness' of the unborn foetus, i.e. life. The fact that as Creator, God is also the Owner of each (human) life, obliges us to protect that life. The more vulnerable that life is, the more it is entitled to protection. It is assumed that human life is endowed with a soul at conception (considering the relationship between body and soul) and on these grounds the termination of pregnancy is rejected at any stage.
In Genesis 9:6, the Lord warns Noah: 'Whoso sheddeth man's blood, by man shall his blood be shed: for in the image of God made he man'. So this is about the situation outside Paradise, and yet man has retained God's image. It is corrupted by sin, nevertheless. When human life begins, God's image begins. That is impressive! For the beginning of life it also holds: The LORD gave (Job 1:21). It is only the Lord who may take it away. There was not only a spiritual recognition between the two unborn children when Elizabeth and Mary greeted each other, but in the original the word translated here with 'babe' (Luke 1: 41 and 44) is the same as the word that is used for a child who has already been born.
There is just one sad circumstance in which (based on the Reformed tradition) a pregnancy may be terminated and is even mandatory: when the pregnancy threatens the mother's life.