I'll agree that that can be hurtful, too, Hmmmmm, and that questions like, "Okay, who here has parents who are absolutely driving them *crazy*?" can be very painful to somebody who has lost their parents. And I would certainly hope that if somebody knew that a friend had lost her parents, it would be unkind to say such a thing, especially as directional as that (whereas I would consider somebody just talking about how her own parents were driving her crazy, while it might still hurt to listen to, more along the lines of people talking about their own pregnancies or childbirth in general), I think it might occur in a general conversation where people don't know. The pregnancy question is, I think, more likely to be a problem for more people (as I mentioned, not just for the infertile, but for other women in different situations as well), but especially as a group ages, the parental thing may be true for more and more people.
There's still a part of me that somehow doesn't see the two things as being the same, but I can't pinpoint why I have more of a problem with "So do you think Mary's gonna be the next to get pregnant?" versus "So do you think Mary's mother is going to come over after the baby is born to help out?" Maybe something about the personal aspect of pregnancy, the woman's body, the Scrabble that leads to it, I don't know. It does feel more gossipy, more digging for news, than just talking about somebody's parents, but it's hard to say why.