"Threatened miscarriage "

I will be 12 weeks pregnant tomorrow. I experienced quite a scare while at work this morning and was taken to the ER. Turns out that my baby is currently fine, and has a heartbeat of 158; however, I'm experiencing what is called a "threatened miscarriage ". There is a 50/50 chance my baby won't make it. Along with many needed prayers, I'm posting this to find out if anyone has experienced this or knows someone that has with a positive outcome. I am so nervous and afraid of losing my child.