I'm still curious about how often you think miscarrige is the woman's fault. It's true that a woman can do things to increase or decrease the chances of miscarriage, but I do not think women are often to blame for their miscarriages. So even if laws specificly protecting the unborn were passed, it would not be prudent to investigate miscarriages. I'd say the same procedure should be followed as with any old person who dies of apparent natural causes. It's not unusual so it's not suspicious.

You're right that if abortion were illegal, people who had illegal abortions could claim they were miscarriages - but why would they let people who would oppose them getting abortions know about the pregnancy in the first place? It would be a really weird and rare situation where there would be a reason to have an investigation. I'm not saying it would never be worth investigating - just as today a miscarriage could be investigated if the woman suspects someone slipped RU486 in her food - but it would be unnecessary in the vast majority of cases.

What would I have done with women who have illegal abortions? Balance justice with the needs of society and look at each case individually. A woman who has an illegal abortion is not dangerous to the wider society, is likely under great personal stress, and is likely not to believe abortion is murder. These factors are all reasons for more leanient treatment. That last one may change over time as society increasingly recognizes that abortion is the killing of a human person, so maybe after a while sentences should get harsher. Hopefully the second would too - society needs to provide poor women who get pregnant with better choices to reduce the desire to get abortions in the first place. I would probably advocate heavy sentences (decades) for abortion providers and serious (years) for recipients of abortion. There'd be a lot of variation in individual cases.