Does an expectant mother have the right to chose the position she gives birth in?

My wife is pregnant and due in about 2 months! We have been doing research and collecting information on the whole giving birth process, and we read in a Lamaze magazine about various positions to give birth in. The magazine suggested that the traditional "lie horizontal on your back with your feet in stirrups and push against gravity" position was not ideal, and has many disadvantages.

Of the other positions we saw, and have researched and heard about, a position of lying on your side seemed to be the ideal one for us. My wife has difficulty breathing when lying on her back and does so much better on her side, and it was suggested that this position can reduce the chance for needing an episiotomy. There were several other advantages to this position, and a variant of it with her body slightly elevated seems like it would be even better.

The problem is that our doctor seems rather unwilling to allow her to give birth in any other than the traditional "lay back and stick your legs in the air" position. We tried talking to him about it, and he did say that she could be in any position she wanted for the first stage of labor (when the cervix is still dialating). But for the second stage, the actual pushing and giving birth stage (the one we are concerned about) he insists that my wife assumes the traditional position. My wife particularly finds this very unacceptable.

We thought about the idea of changing doctors, but in the birthing class today the nurses (at the same hospital as our doctor) seemed to indicate that all the doctors at our hospital keep to this practice (despite the class covering alternative birthing positions), and with our particular insurance (Medicaid) changing doctors now would be very difficult. Add to that that we live in a small community, there is only one hospital anywhere nearby and our doctor choices are very limited. Being of low income limits it further. And, aside from this one point of contention, we like our doctor.

So what rights does my wife have? How can we assert those rights? Is there anything else we can do? My wife is very uncomfortable and frustrated with this situation and I join her in at least the frustration part, but after trying to talk to our doctor once we feel somewhat helpless.

If the information is relevant, we live in Missouri (in the United States) and my wife has no other medical insurance other than state medicaid for expectant mothers. Obtaining other insurance would be completely out of our budget, as we were barely able to buy groceries this pay period, and our savings has been recently drained due to surprise expenses. What extra we will have on my next paycheck will have to go straight back into rebuilding it.

References and links are welcome, as always, as are personal experiences and knowledge. Thanks for any info in advance and God bless!