Helen's child becoming the eventual heir of Howards End holds much in way of symbolism. The first element of symbolism is that Leonard Bast ends up being represented in the world of the Wilcoxes. Despite Henry's attempts to silence Leonard Bast and Charles' attempts to erase him from memory and record, the child that he fathered with Helen will play a role in the narrative of Howards End. It is symbolically important because it shows that the wealth and power of the Wilcoxes could not stop the forces of change in recognizing what is just and fair.
At the same time, the symbolic element of Helen's child being the eventual heir to Howards End underscores this element of social change that is transforming England. The presence of wealth and privilege that stratified English society for so long is changing. An illegitimate child from middle class to lower class parentage is going to be the eventual owner of Howards End, the epitome of wealth and privilege. Howards End will end up becoming the realm in which the classless society can be recognized. In this use of a specific plot device, there is symbolism present.