What is the usual translation of the the terms "pro-choice" and "pro-life"? (More generally, how would one say "pro-X"? I assume "anti-X" is kontraŭ-X-a.)

To the best of my knowledge, "por" or "favore al".

I've seen "por" used as a verb for that, "mi poras la proponon". I think however I would translate "I am pro-X" with "mi favoras X:n". There could be better ways, though. Evidently I do not argue much

I generally support what mnlg said, but I have a couple of comments to add.

First - in my opinion, you could also use -subtena as a suffix in instances like this; viv-subtena, elekt-subtena.

But more specifically, related to anything that is colloquial in nature, I personally like to use Esperanto wording that is a little more descriptive. In US English, these euphemisms "pro-life" and "pro-choice" are generally understood. But in Esperanto, where people aren't always aware of the cultural background behind these euphemisms, I might choose to go with the more straightforward "kontraŭ-aborto" (or "kontraŭ-aborta" in the adjective form), or "favora al abort-rajto" for the other end of the spectrum.

It's a little more wordy than the pithy "pro-life" and "pro-choice" that have come to dominate US political discourse, but I think it's clearer for an international audience (who may understand "pro-life" to mean "anti-death penalty" and "pro-choice" to mean anything at all, it's so vague)

[Hi Umlaŭto! I'm living in Maryland now, but the MIT group is now meeting twice a week, once for lessons and once for conversations, so you can still feel free to drop in whenever you feel like it]

Right, I figured the preferred gloss wouldn't necessarily involve the words "life" or "choice". I was more asking if there actually was a standard name for those two positions. So... "kontraŭ-aborta" and "abortrajt-subtena", or something like that, if I absolutely must have single words?

(Also: Hi, Erinja! I once showed up at the MIT Esperanto study group a few times before I got too [busy|lazy].)

Having both mnlg and Erinja giving their advice before me, I feel a little insignificant to drop my two cents in here, but hey! Do I have to be so proud that I shouldn't ever look bad???

I just thought about the suffixes -ist and -ism, the former as understood in esperantisto and not in laboristo...

But like Erinja mentioned, vivisto and vivismo could be interpreted as a philosophy of live and let live in a very broad approach, or as a position in the death penalty debate, and elektisto (elektismo) could be just about anything...

In the right context, in keeping with Filu's comments, "abortrajtisto" (and "abortrajtismo"), and "kontraŭabortisto" (a supporter of kontraŭabortismo) could theoretically be used. It works nicely with "abortrajtisto" but with "kontraŭabortisto", it might be a little more vague, since it could be understood as kontraŭabort/isto or kontraŭ/abortisto (though this may be too fine a distinction, since presumably those who are against abortion are also against abortionists)