It's important not to conflate all of these cases. They are not all identikit and many different factors are involved.
We don't know until the Serious Case Review exactly what input the mother had and if anything appeared during that input that needed flagging or being acted upon.
This article (trigger warning - graphic) is a look at a case and how it was impossible for the SW to predict what was going to happen: www.theguardian.com/commentisfree/2007/aug/16/adeaththatcouldnotbeforetold
There are lots of not very good parents out there, it isn't necessarily obvious which of them will murder their children.
From the facts presented, I feel somewhat uneasy at the culpable homicide verdict. The recent case of Keanu Shuttleworth, where he was also assaulted and left to die, resulted in a murder conviction. In an even more recent case, that of Callum Wilson, the mother not only received a life sentence, but had her minimum tariff increased as it was deemed unduly lenient.
While we are on the subject of Sharon Shoesmith, while I disagree with the manner of her dismissal, I do think she should have resigned anyway. If that department had been an award-winning beacon of excellence, would she have taken credit for it? Of course she would. Therefore she should accept responsibility when the department was failing so horribly.