Imagine waking up one morning with asthma, rashes, and upper-abdominal discomfort. Upon going to the hospital and having a series of tests performed, it is discovered that you unknowingly introduced a round worm into your digestive system through contaminated food or water.
When you ask to have the round worm removed, the director of the hospital tells you, "Look, we're sorry this round worm has infected you, but this would not have happened if you had been more careful about what you eat and drink. However, the round worm is inside you, and to remove it now would be to kill it. But never mind, it's only for a year. By then it will have completed its lifescycle, and can be safely removed from you."
Remember, all living things have a right to life, and round worms are living things. Granted you have a right to decide what happens in and to your body, but a living thing's right to life outweighs your right to decide what happens in and to your body. So you cannot ever have it removed from you.
Surely, you would regard this as outrageous. Now consider for a moment that eventhough a fetus has human DNA, it is definitionally a parasitic organism:
par·a·site n. An organism that grows, feeds, and is sheltered in or on a different organism while contributing nothing to the survival of its host.