And there were slaves who regretted abolition too, but that didn't justify a continuation of slavery.
I've never met a woman who decided to let their baby live and regretted that
Then you've probably never met any women whose children ended up in prison, because that's where most of the unwanted offspring end up.
How can motherhood really be compared with slavery?
I didn't compare motherhood to slavery, I compared forced motherhood to slavery. Similarly, I wouldn't compare sexual intercourse to slavery, but I would compare rape to slavery.
I doubt there's any evidence that those in prison were "unwanted pregnancies", many were welfare babies, their mothers didn't abort them for different reasons ---a nice welfare check being the main one. When women have babies for the welfare, they don't even consider abortion but they also aren't making an effort to raise them. I know of quite a few children who were from unplanned unwanted pregnancies whose mothers don't regret having them, the kids are doing very well and never went to prison.
Anyhow if your argument worked the prison population should be sharply decreasing since 16-18 years after Roe v Wade and we know that isn't the case.