There is a lot of research into certain issues - early trauma, autism, foetal alcohol syndrome, various generic conditions, all sorts like that.
But there will always be a huge amount of uncertainty.
For example with a child who is delayed meeting milestones, that could be due to neglectful early experiences, it could be due to learning or physical disabilities, it could be due to trauma. It might be that the child will catch up completely, but it might be that they will always have those delays.
You'll never know for sure that a ba baby hasn't been exposed to drugs or alcohol in uterine (although you may know absolutely that they have). There's now evidence to suggest alcohol abuse by birth fathers may cause FAS as well as by birth mothers, and it's possible you won't know who the birth father is at all.
Differing children react to trauma in different ways, some may be only minimally affected and some may have lasting and profound issues as a result. And a child who appears to be only minimally affected at 2 or 3 may develop major problems when they hit puberty. Or they may not.
Even when you think you know, you may not - for example a friend adopted a child who was diagnosed with cerebral palsy. But that child started deteriorating, and has in fact now been diagnosed with a progressive and terminal childhood illness. Conversely another family adopted a child with cerebral palsy and global developmental delay, and that child now has no physical issues at all.
One child who has experienced early loss may push away adults and turn inwards for support, trusting no one. And another may be scared of independence and remain overly childlike and clingy, afraid to do things for themselves in case the next parents disappear too.
There aren't guarantees. Hopefully though if you're looking at children's info, your SW or the child's - or a paed if there are complex issues - should be able to give you at the very least a "we don't know for sure, but we often see this, that or the other as a result of this condition/issue/experience."