My baby girls movements also decreased at 30 weeks my OB said it is very normal as long as I feel some sort of movement, your baby's probably just going through a growth spirt and getting some rest:)
I have just gone 30 weeks today and since Wednesday I have noticed my boys movements decrease a lot also! He used to wriggle and jump around now I only feel twitches and small nudges. If it makes you feel any better I went to hospital Wednesday to get him checked just incase and he was fine, I'm still a little worried but they may just be growing so tired out! I'm sure it's fine.
My baby girl moves a lot one day then the next couple of days she barely moves
Baby is starting to run out of room but if your worried lay on your left side and do a kick count. 7 movements in an hour is completely normal even a little less
I am 19 weeks and 2 days and I notice it too. My little girl used to move a lot too, but the last few days she doesn't. I am in a grow spurt and so i heard that when they grow they don't move so much.. But I don't know if that's true. If you are not sure call your doctor or midwife. Good luck!