Well, let's try to put the best spin possible on the Libertarian position, shall we? I agree with you that the right contains very few actual Libertarians, but let's have a go. Let's construct the best argument we can for them.

Everyone should get to decide what to do with their own bodies, according to Libertarian principles, including making agreements to do or not do certain things with their bodies.

If someone wants to cut off their own finger, that's their business; we don't stop them. If someone wants to cut off someone else's finger that's totally different and we have to stop them at once. If two people enter into an agreement that one can cut off the other's finger, also fine. Suicide: fine. Murder: no way. Assisted suicide: fine.

Okay, but what if you can't actually accept the agreement? Then, generally the idea is that the person's best interests have to be followed. So, for instance, if you pull an unconscious drowning victim out of the water, you can perform mouth-to-mouth resuscitation (otherwise a clear violation of bodily autonomy), but you can't have sex with (i.e. rape) them while they're unconscious.

So far so good.

So women, as people, can decide what to do with their own bodies, even if it's cutting off their own finger or having an abortion.

Except!

What if the child is a person?

Now we're in trouble. The child can't demand anything from the mother nor can the mother endanger the child without an agreement. But of course the agreement can't be made explicitly...and the "best interest" of the child is (assuming a lack of genetic or developmental abnormalities at least) to live.

Now, if the mother willingly had sex, you can point to that and say: there. That was the implicit agreement of the mother to gestate the child. She agreed, the child's best interest is to agree; she can't break her agreement now.

("Willingly" includes having the cognitive capacity to enter into contracts of that signficance--usually adulthood.)

If the mother didn't willingly have sex, and the child is a person now we're in Libertarian nightmare territory. The at-fault party (man) has set up an existential conflict between two other people. We can kill him, or whatever else we think is appropriate. And we still have this horrible direct conflict between two hugely important rights. This could go any way and be roughly equally as reasonable.

Now, all this is contingent upon the idea that the child is a person. If the child is instend considered property (or part of the woman's body), then you either get full abortion rights or, in the case where the child is considered the father's property also, full access to abortion if the partner consents (or the sex was not consensual to begin with).

So, anyway, here's what you need for your Libertarian to self-consistently have a strong pro-life stance.

* Sex is a consent to a contract between child and mother for the mother to gestate the child, if any.

* Personhood begins at conception.

* Life is in the best interest of a baby.

* Don't talk to me about lack of consent; that's too hard LALALALA

Obviously the two first points are arguable, and the last isn't even a point. But it's not the case that Libertarianism has nothing useful to say about abortion, even about a pro-life stance.

There is a sensible, consistent, strongly anti-abortion, completely Libertarian position, providing that you accept the ideas of sex-as-contract, personhood-from-conception, and life-is-best-interest.

(Libertarians still have to be 100% in favor of allowing birth control.)