Can I offer up some friendly advice? I know sometimes when you haven’t experienced something, it can be hard to know what to say. So if you know of a woman who’s had a miscarriage, please avoid saying things like “It wasn’t meant to be,” “God must have other plans,” “At least you have the other kids, be thankful for them,” or “I understand”. And please don’t suggest possible causes or try to diagnose her. Those things all tend to hurt more than help.
Instead, just simply say, “I’m so sorry, is there anything I can do for you?”, and listen, if she wants to talk. That’s an across the board acceptable response that shows you care and that you’re a safe person to come to.