As hard as it is there are some things we can say to help the situation. First, try "Thanks! I needed one more entry for David Letterman's Top 10 Stupid Things People Say to Somebody Whose Baby Has Died". You can only pull that one off if you have a great sense of humor and the person you're saying it to does, too. Or you hate them so much you don't care about how much you're going to * them off.[:p]
OK, so now for my serious answer.
Usually people really do NOT know what to say and their first error is just staying away, ignoring you b/c they're so uncomfortable with the situation. So, if somebody does actually approach you with a choice comment from the David Letterman list, do your best to respond gracefully with the idea that you have an opportunity to minister to them. You have had a life experience that they have not and can be the teacher, in the same way that we are all both students and teachers of life. By expressing respectfully what you believe or feel about their comment and also sharing how much their support means to you, you help break down the barriers and make it easier for them to truly support you and better for next person who could be comforted by them. It's a "pay it forward" thing.
Here's a great umbrella idea to nip all these in the bud. If you have a chance to do a funeral or a memorial or anything that might give you the podium for a few minutes, then take the opportunity to preempt the "stupid comments" but addressing them generically. i.e., "I know it is sometimes said that... but in reality..."
Some ideas, based on my own experience with "stupid things..." (note: in the immediate aftermath when I couldn't take a breath without crying, these answers were irrelevant. In those cases, vent with your DH and curse liberally! If you have a long-term relationship with the person and don't want to harbor ill will, you should probably double back with them later and say, "You know, I've been thinking about what you said, and at the time I was so hurting and confused I couldn't process it. Can we talk about it?)
"It was God's will." -- "Actually, it wasn't. The God we believe in (to a fellow churchgoer) is a god of love and light and perfection. Death and preeclampsia aren't part of his plan. What I do believe is that God's will is the love and support that we're getting from this community. I really appreciate you being here for us. (hug) Please don't ever believe that tragedies like this are part of His plan. It will be so hard on you when you have to suffer something difficult."
"You can always have another." -- "Maybe. Maybe not. Regardless, nobody will ever take Nikonia's place and we really appreciate you remembering her and us in your prayers. (other variations: "At least you have other children.")
Some of the "rude" comments from mothers and MILs are usually disguises for their own grief. They can't seem to stop being mothers and giving "advice", but in reality, they're hurting too and, for once (LOL), may not know the first thing about what they're talking about. Cut them some slack, educate them and ask them (later when you're more stable) to share their own grief journey with you. "What was it like when you heard your granddaughter had died?" "What did you tell Dad?"
Well, I could go on and on, but that'll have to wait for the book. You get the idea. The jist is this: be hurt, be pissed, but recognize that we have had a unique life experience, that most people don't have. What we do with it is our choice. We can be lights in this world, or continue the tragedy of ignorance - either of this disease or of the grief associated with this kind of loss.
Before hitting send, I re-read this and realize that it could sound pretty Pollyanna-ish and if you're grieving and angry, then this sounds like a bunch of psychoanalyst BS (which I'm not, btw). Just know this: I've been there, sometimes still am, people pissed me off, sometimes still do. Some I've never dealt with (or at least not well), many I have dealt with either through the "preempt from the podium" approach or 1:1 - and I have never regretted it one day. On the contrary, I have engaged in very meaningful, healing conversations, at least to me and often to them, too.
If this was helpful, let me know. If this was hurtful, let me know that, too.