Penalty for not paying an OB/GYN fee?

I am 32 weeks pregnant, and the receptionist at the OB/GYN I use decided to tell us at my 26 week appointment that we will owe my doctor $2500 for the global delivery fee and it is due by my due date (April 21). She said no insurance covers the fee and it must be paid by April 21. I feel it is very unfair for them to wait SO long to tell me about the fee, and expect my husband and I to have no problem coming up with $2500 in 14 weeks with no problem. The same time she told me about the $2500 she also said "Oh, well you should have paid us $850 last time you were here to make a payment towards to fee to put in a holding account". How could I have paid the fee if we didn't even know about it? And they are acting like we just have this money laying around! I asked her if it could be added to the hospital bill and be paid in installments and she said no. I asked if there were any payment plans available and she said no. My husband and I have already talked about it and we are NOT going to have $2500 by April. We have other bills to pay and that is just too much money for us to save in such a short time frame. Any advice on what to do? Can my doctor report us to collections? I have an appointment this coming Tuesday and plan to give her a piece of my mind about waiting so long to tell us about the fee and let her know we won't have the money, but wanted to get some ideas from here first. Thanks in advance.