80,000 Hours has a cause quiz, possibly a bit dated and sometimes a bit buggy (sometimes you see the rankings during the quiz, sometimes you only see them at the end, and sometimes there's an extra question).
Question 4 is particularly relevant fvor person-affecting views, but it might not get at your specific views, since there are many different kinds of person-affecting views:
Question 4: Here’s two scenarios:
A nuclear war kills 90% of the human population, but we rebuild and civilization eventually recovers.
A nuclear war kills 100% of the human population and no people live in the future.
How much worse is the second scenario?
Besides the causes listed there, there could also be mental health and pain relief, and since you think death is bad, cryonics and life extension.
Whether or not you think it's bad to bring absolutely miserable lives into existence (the asymmetry), that could have important consequences. If you do think it's bad, then the longterm future could matter a lot.
Your response to the nonidentity problem also matters. Essentially, do you think if either A or B will be born, and the value in (total quality of) their lives will be X and Y, respectively, with X < Y, does it matter to you whether A or B is born? Is this the same to you as whether A is born and lives with value X or Y? As an example, if a couple wants to have a child, but the mother has been infected with the Zika virus, considering only the effects on the child, should the couple wait to conceive until it's unlikely the child would be affected by Zika? If they wait, a different child will be born. If you don't think it matters whether A or B is born, regardless of X and Y (even if one or either would be miserable), then basically the longterm future shouldn't matter to you.
If you do think it's bad to bring bad lives into existence or that it matters whether A or B is born (considering only their interests), then the longterm future could still matter a lot, and assuming you do focus on the longterm future (you might still have empirical doubts) your focus would be on preventing s-risks or ensuring its quality is as good as possible, conditional on moral patients existing, but not ensuring moral patients exist for their own sake. See the link about s-risks, trammell's answer about this paper, or the talk about that paper here.
The linked opinion piece asserts that abortion regulations are not responsible for the improvement, but doesn't seem to provide any evidence to back it up?
I am not that familiar with the literature, but it would seem prima facie rather implausible to me that making something illegal wouldn't help reduce its prevalence. If statistics suggest the US decline is being driven by other policies, I would guess this is because the restrictions that have been put in place are quite weak - abortion-for-convenience remains legal in all 50 states, and even a your state did impose some limitation, they cannot stop someone travelling to an unregulated state. However, a quick google suggests that some academic research does find that the restrictions that have been put in place have helped reduce the rate. Additionally, it seems that the number of abortions in Ireland has gone up significantly since their law change, even taking into account people travelling to the UK, so presumably reversing that change would help reduce the number. This also fits with my impression of what has happened in other many countries when they banned/unbanned abortion.
I totally agree that reducing miscarriage rates could be very interesting. Are you aware of any tractable interventions? I had a little look a few years ago but did not find anything very satisfactory.