I had a friend who just hugged me when my mum died, I remember that more than most, it meant the most he mubbled I don't know what to say, 6 months later I had to do the same for him when his dad died, I remember the people who said nothing and actually avoided me, they I have now pegged in life as weak people, you don't need to say a bloody thing just show you care.
I had a work mate whos daughter was still born years before this, and I went throught what you are going through, a week after the death we had our work party on a boat and him and his wife came, after an hour of going past them to the bar, loo ect I realised that not only me but everyone was ignoring them, and they had no escape as it was a boat on a cruise! I mentioned it to another friend and she agreed she was doing the same, she then grabbed hold of me and dragged me to their table and asked if they wanted a drink, she then went and brought the drink, smart move leaving me with them :/ anyway after a few mins of silence well thats what it felt like, I just blured out, I am really sorry, my Mum is a midwife and she said the problem with still births and miscarrages is you can't talk about them as thought they exsisted, because you can't talk about their smile the food they liked....and I rambled on for an age, eventually A just smiled and said, relax, we knew tonight would be tough and you are the first person to talk to us, we understand, and relax, they then explained that they did have something to talk about, the pregnancy and they way their daughter used to stick a foot out all the time :) so it showed on Mums belly, and then she would do sommersaults after mum had eaten... I am alway greatful to my firend for dragging me over and offering the drink and running away, because I got all the kudos for being the first, but actually I was Shit scared, and forced into it, I have never worried since.
basically what I am trying to say is just go round and you don't need to say anything, just make tea, make sure they eat and be there.