Signs are severe cramping (or even slight cramping) bleeding and clots usually.

yup like a really really bad period

Not all miscarriages are a like. Some have an extreme amount of pain.....Some don't. Some have a lot of bleeding.....Some don't.
Do you feel like you're having a miscarriage? If you answer yes you need to see your doctor asap.

Ya just go to the doc

*lilpattycakes*

well I have had two miscarriages the first one wasn't as bad as the second one. The second one I was at my older brothers house with him and his 3 room mates and a couple friends. They were all drinking and I had to go to the bathroom to throw up. So I threw up and I guess when I walked out of the bathroom I passed out. Everyone thought I was drunk but I didn't drink not one drink at all that night because I knew I was pregant. I really don't remember the rest the only things I could remember if bleeding a lot and wking up in my boyfriends bed with extremly bad cramping. Well thats my story on my miscarriage! Hopes it helps you out!

It all really depends on how far along you are.

Miscarraiges that happen in the first few weeks usually are like a period with bad cramps. But the farther along you get, the worse the pain can be.

If you are pregnant and you're passing a lot of blood and matter then it can be very serious.

You can have a little pain, all the way to actual birth contractions. It all depends on how far you are...

The hospital can check when you go into the er and they test your hcg levels. If they are very high, they will test again to see any significant drop. If you are lower than usual, they will most likely assume you've had a miscarraige.

Unfortunately, if you're only a little far, they can't do anything to stop it. But if you're farther along (2nd tri, etc) they can try to stop it the best they can.