Short answer: Invalid question
Long answer: Does your question mean the fetus exercising coercion by "stealing" nutrients from the mother based upon its needs for survival? Or do you mean when a fetus is taken to term and the mother gives birth to a baby?
Both of these questions don't take cognizance of the full nature of a fetus. The answer to this question can be arrived at from a clear answer to a different question: what is a fetus? A fetus is a biological entity not separate from the mother. It is not a separate being apart from the mother and does not warrant any political distinction apart from the individual rights of the woman. It is in the nature of a fertilized egg to attach itself to the wall of the female uterus and grow by means of nutrient absorption from the mother into a baby. This is not a physical threat against the mother as this is the natural course of child birth dictated by the identity of the female reproductive system and corresponding fetus.
As to child birth which can be a painful and laborious process hence the name "labor", this too is a natural and expected occurrence. It should be advised that one not equate pain with force. It is not a simple reduction and so therefore cannot be equated.
In fact what is most important in all of this discussion is the fact that a pregnancy can occur from many different ways which are voluntarily chosen. Discounting rape a woman only gets pregnant if she chooses to have sex. And any pain, discomfort, sickness, or life threatening situations which may occur are all present in the decision to have sex and get pregnant. So it would be quite an evasion to think that a fetus comes out of no where and starts initiating force against its host mother. How did the fetus get there in the first place? And addedly lets not forget that a fetus is not a fully conscious being that itself chooses to be born. It has no say in its existence. It was brought to life from two separate individuals.
Lastly I would also point out that the initiation of force is a ethical/political distinction not metaphysical one which this question assumes. To attempt to apply this concept would be mixing categories which doesn't make for clear answers.
answered Feb 20 '11 at 00:56
The fetus is there at the will of the mother. If she is planning to carry the pregnancy to term, then she is choosing to use her body to sustain the fetus until it comes out, and she is choosing to go through both the pleasant and unpleasant aspects of pregnancy and childbirth (and parenting, too). Since this decision (to remain pregnant, to carry to term) is entirely hers, the idea that the fetus is initiating force is nonsensical.
answered Feb 20 '11 at 10:28