In order to turn someone, you have to completely drain them, but at ehe point of death, you have to share your blood with them. Then they die, and resurrect as undead vampires. Since the change requires the victim to actually die, the unborn fetus would also die. Even if it were to somehow turn with its mother, since a vampire never ages, depending on how well developed it was at the time of turning, it would either remain in an embryonic state, or never develpo beyond an immaturely born infant. If, on the other hand, by some miracle the baby were taken immediately after the mother's death and put in an incubator until it had developed well enough to live on its own, then it would be completely human, with no Blade-like powers, because the powers come with the rest of the vampire package, the first requirement of which is for the host body to be completely and permanently dead. No death. No death, no vampire powers. But if it makes you any happier, you could still kill it by cutting its head off, burning it completely, or driving a wooden stake through its heart.
