couple questions about 3D ultrasound

I have to get an ultasound my next appointment (May 2nd) where I'll be 30 weeks because they found on my 20 week scan I have placenta previa(I switched doctors and my other doctor never said anything about it) so I was wondering do you think they'd give me a 3D ultasound that day to? I know I'll just have to ask, but just wondering since it's last minute if anyone was able to do that. And my biggest question is I have Medicaid so would they pay for the 3D since it's not necessary?