just plain fascination. Perhaps those who have gone through pregnancy have forgotten how they viewed and interacted with pregnant woman before their own experience?

At the risk of sounding like a total stoner, it's pretty trippy to think that a real human being could reside in the body of another human being. Yes, I realize that we have all had plenty of time to absorb and accept this concept but maybe it's fascinating because it's not as common a human experience as, say, breathing.