Siarie, will answer your question but just wanted to put a warning that it might be upsetting for some people to read so be warneedddd and don't read if you get too worried about things/might get upset
I was 32 weeks. Since my 28 week appointment I had been telling my midwife at the time that she wasn't moving much. The midwife brushed it off and said it was normal as she was my first and I had an anterior placenta. She then went to listen to the heartbeat and it took her a while to find it, it sounded wrong. It was slow and quiet. I said that to her but she said it was normal. As she was the midwife and it was my first I had no idea so trusted her. I then went to my 32 week appointment and someone was covering for my normal midwife. She tried to find the heartbeat and struggled, then I heard the same as last time but she said that was my heart beat
she sent me straight to the hospital for an emergency scan where they confirmed that my baby's heart had stopped beating. I was then given lots of tablets to and told to come back in two days to be induced. I went into labor myself the day after whih was horrendous as I had to go to the normal labor ward. I remember hearing babies being born in the next room and when my baby was born the room was silent, there was no screaming, just quiet 
I was then allowed to dress her and spend some time with her, I was given her hand and foot prints and a memory box and then I said goodbye to her so she could be taken away for a post mortem. She was later cremated and buried with my nan.
They never found any cause for what what happened, they said it was 'just bad luck' that my placenta failed. They couldn't say whether it was likely to happen again that's why they kept such a close eye on me this time. they did confirm that my dd had passed away inside me around 28 weeks so she had already gone when I said there was something wrong but I was still feeling slight movements as she would move in her waters when I did.
I would just say if EVER you notice ANY change in movements at all or even if you just feel there's something not right call the hospital and go there. Don't take no for an answer. It was the worse time of my life and no one should have to go through that 
sorry for the long post.