Says the psalmist David: “You kept me screened off in the belly of my mother.

Ps. 139:13-16, NW; compare Leeser’s translation.

Clearly, God viewed David’s embryo as a separate entity. The Encyclopædia Britannica agrees: “The life-history of the individual, as a distinct and biological entity, begins with [fertilization].” In fact, a human embryo is so “distinct” from its mother that her body’s immunological defenses would reject it as foreign if nothing interfered. But special “trophoblast” cells and later the “placenta” protect the embryo, to keep it as if ‘screened off in the belly of its mother.’