The problem for CW is that his story, of flying into a rage and strangling his wife, THAT prevents him of ever saying he tried to save the girls.
He says SW was 'active;ly strangling' the 2nd child. Thus the child was possibly able to be revived, given medical help.
But by spending those precious several minutes, strangling his wife, and killing his unborn son, he is allowing the certain death of his 2nd daughter.
He cannot ever say that he tried to save his daughter, because his story prevents that from happening.