A.T.
Having been through a miscarriage myself (first and only pregnancy) here is my advice: Don't really say anything but "I'm so sorry." People always want to say something that will make the person feel better, but truthfully, nothing any one says can take the pain away. Only time can heal this kind of wound. Allow them to grieve the loss of their child(ren) as you would anyone who lost a child, and let them know that you are there for them, whatever they need. That's what others did for me that was the most helpful.