A better means would be to not lay with a man if you don't want to become pregnant.
Exactly. The natural right to control your own body is preceded by the natural DUTY to control your own body. If women controlled their own bodies, 99% of unwanted pregnancies would not occur. (I'm exaggertedly claiming that only 1% of pregnancies are due to forcible rape. Even Alan Guttmacher would agree it's less than that.)
"If you don't want to make a baby, don't do the baby-making thing."
"Control your own body. A pre-conception right." How about those as slogans for Libertarians for Life?