Elves are born with different amounts of mana, which increases as they age and will determine their potential of magical power. Elven maidens with large reserves of mana usually produce powerful children. Mana is transfered from the mother to the child through the umbilical cord during pregnancy. Under normal circumstances, the baby feeds of this mana to grow over a period of nine months.
However, abnormalities can occur during this process. Normal interaction between fetus and mother causes a small irregularity in the power structure of our own dimension. Dark entities can take advantage of this in rare cases, ripping it larger and turning the fetus into the equivalent of a mana black hole. Mana is pulled towards the fetus and leaves our dimension entirely to feed the parasite. This new parasitic child is referred to as a dark elf. The unborn child sucks the mother's life force faster than she can regenerate it, draining her completely and turning her into a husk.
The parasitic entity seeks to use the child as a conduit to feed on the mana of others. However, the effect it has on the parent becomes evident due to the effects. As it becomes obvious what the child is, it would naturally be aborted in order to save the mother's life and to prevent it from causing further damage in the world. Even if the child is born, it would be immediately killed, being recognized as a monster. This would deny the entity its vessel and rob it of the mana that it seeks to feed on.
How can this entity ensure that its vessel isn't killed so it can survive to adulthood?