This whole "pregnancy scare" sounds like a crockful to me. Firstly, if it happenned (which is not impossible) how did anyone besides these two know if William was shocked at the news??
Then if we assume it happened a few weeks ago this is about the time he was photographed at the night club before the departure for the bike races.. Can we believe that after all these years, he left her worrying and went clubbing then off to Africa with friends?
Apart from all this, if there was a scare and he is not scared yet, it must be true love and he intends to marry her someday.