Hospital Prepayments

Andrea
Does anyone else's doctors office require you to have your ob visits, postpartum, and delivery paid in advance? 
My doctor office wanted me to start paying as soon as I confirmed my pregnancy, and have t paid off by 8 months. I told them I was waiting because I was almost at my deductible. I just don't understand why they would want it prepaid....doesn't that have to go through insurance??