Blood test to detect baby's blood in Mine.

Hi,

I am wondering if anyone has any experience with this. This morning i could not feel baby moving for a few hours and went to the hospital to be monitored. Everything was fine. Baby started moving and heartbeat was fine. I however have to go back to the hospital to be monitored again tomorrow and to do a blood test to see if there is any trace of baby's blood in mine. From what I understand if there is then I might be induced. I am 35 weeks tomorrow.