35 weeks going for amnio for lung developement on tue 36.1 weeks?

im going for an amniocentisis on tuesday for lung maturity test since i have mild pre eclampsia and it seems to be getting worse and doctor wants to deliver but wants to make sure baby is ok..so heres my question. has anyone else had this done? and is it painful, as my doctor says they dont numb you and it takes about 5 minutes to do.. is that right? and what has been your experience. thanks