What was the point of . . . [spoilers]

What was the point of having Ana be pregnant? I assumed that Bruno and Berta had selected the young couple because she was expecting and that they were going to do some heinous thing involving the baby (although they did the next most heinous thing in American culture, which was to kill a dog). However, other than Ana's pregnancy being mentioned at every possible opportunity, it had absolutely nothing to do with the satanic plot against the unsuspecting pair (or anything else for that matter).