Lois impulsively spilling the beans about her pregnancy seemed like the exact sort of thing she'd do. She should wait to tell her parents for as long as possible - definitely until after she and Clark have fully come to terms with their relationship. I somehow suspect their reaction will be less than positive. Clark's clearly emotionally fragile right now if he reacted that badly to Ralph's comments. At least Lois told him that she loves him...that's a good sign.
