At 27 weeks I had a real slow down in movement and when I posted I found that a lot of other ladies had the same during their 27th week. I found that interesting. When asking my doctor about it she explained to me that she doesn't even ask moms to be to count kicks until they hit somewhere around 30 weeks because babies movements can still be so eratic at this time.
She also explained that babies can have restful periods, particularly during a growth spurt, so where a bunch of ladies, myself included, had slow downs during week 27 maybe that's a major growth spurt week!
Things you can try in order to get baby going if you're worried:
Drink ice cold water
Drink something sugary-soda pop or Apple juice
Eat something sugary (nice excuse!)
Lie down on your left side
You should feel ten movements in an hour. Movements can be anything from a major kick, to a minor little shift in baby's position.
Try not to worry, best of luck to you.
p.s. I did have a scare of my own yesterday where baby moved, but the movements had changed and weren't as strong as before. I put a call in to my doctor's office and she explained to me that as long as you feel movement everything should be okay. If you go for a long period of time without movement at all, even a day then it's best advised to go in. This is obviously after you try whatever tricks you have in order to get baby wiggling.