According to the Dynasty thread this bug is still alive and well. It can strike for any single sim who is teen or older, to any gender. This is due to the way Foreign sims propagate themselves. They do not have to have a romantic relationship in order to have a child, and when your sim meets them they can instantly spawn a baby (except that they don't have babies, they just pop out full grown children, no pregnancy necessary).
The only way to avoid this bug is to avoid traveling with your single sims. If they are married then for some reason it won't happen, but if they're single... WATCH OUT!