I don't frequent the forums... I mostly just check to see if there are any updates from the episode release guessing games... So forgive me if this has already been mentioned somewhere. Secondly, I haven't heard anyone else mention this outside of the ttg forums either (but then again I've only watched one lets play of TWD)
My theory is that Christa is pregnant. It explains why Omid was so happy to see a child, it also explains what he and Christa were discussing when you got to the top of the overpass and (if you helped Omid onto the train first) why he was so extremely upset that you didn't help his uninjured girlfriend first.
What do you guys think??