I agree with previous posts - this is a process that can be really scary and overwhelming for your wife - so treating her like she is in charge and her needs matter more than anything else will help her feel more supported through the birth. Listening and accepting what she says no matter what it is will make a huge difference!

Having my Mum in the room with us at DDs birth made a huge difference because she was using her 'psychic' mothering instincts with me (getting me water, bits of food, talking when I needed to and shutting up when I needed quiet) - while my now ex was more interested in the machines and stuff to help much at all - I was grateful that he was there though, he just wasn't focused on helping me.