If the blood was in your urine and didn't come from your vagina it is not possible to be even a threatened miscarriage. Blood in the urine (or hematuria) is frequently a symptom of a urinary tract infection. Call up your provider to explain your symptoms and ask to be seen so you can be properly treated. Don't go rushing off to the emergency room - totally not worth the strss, the wait, and the expense.
Oh, and if the that little bit of blood may have come from your vagina but you don't know for sure - just keep an eye on it. If you're not actively bleeding, if it was just a little spot, then mention it to your provider but don't worry. It can happen for lots of reasons (including a slight strain from lifting a kiddo) but if it doesn't continue there's nothing to worry about. Don't fret. You'll be just fine. Still no need for an ER visit unless things get significantly worse. Just call your doctor's or midwife's office to talk to someone if you're worried.
I would go to the hospital to be for sure but blood and cramping sometimes means miscarriage I'm not trying to worry you but it happens so go to a doctor to check on the baby