The encounter with Amavia in Book 2 might be one of the saddest in the whole Faerie Queene. Dying in the forest with her newborn son, Ruddymane, and her dead husband, Mordant, Amavia's pitiful condition is what spurs Guyon onto action against Acrasia.
This tragic family, directly and indirectly victims of Acrasia's lust and loose-living, represent the dangers that getting involved in that kind of life can pose. Specifically, their encounter with Acrasia depicts the threat of venereal disease (i.e. STDs, before they were called that).
Mordant, by becoming involved with Acrasia sexually and by drinking a potion she givens him, is infected with an STD that he passes on, unknowingly, to his wife. Even their son, born in blood, carries some of his parent's guilt with him, represented by his permanently blood-stained hands (which is where his name comes from: "ruddy" meaning red and "mane" meaning hand).
The image of Amavia covered in blood and holding onto her infant child is also a kind of inversion of the Madonna and Child image, an image of the Virgin Mary holding the baby Jesus that is frequently reproduced in Renaissance art. This make Ruddymane a representation of the object of Jesus, who died for the sins of all humanity, so it makes sense that Ruddymane's hands would continue to bear the mark of guilt as an emblem of the guilt all humans share.
Ultimately, though, that what's particularly tragic about these characters is their combination of innocence and guilt. Unlike many characters in The Faerie Queene who are pretty black and white, Amavia and Ruddymane embody how sometimes, bad things happen to pretty regular people.