Under the law, the fetus is not regarded as having its own "life" until it is separate from its mother. Therefore, a fetus can never be a "human being" because it becomes one when it is born. However, in some jurisdictions, it is regarded as a separate being if the mother is attacked. So, if the mother was killed, the killer is sometimes charged with double homicide. Please note that you are stepping into a legal and moral quagmire.