Amnio at 36 weeks to check lungs?

Ok I have been having contractions 3-15 mins apart for about a week and a half I'm 35 weeks and 1 day and one of the doctors that I seen told me to talk to my doctor about doing an amnio at 36weeks to check lungs for maturaty. What are the risk? Benefits? I know if is ok then they can induce but they told me they can't legally induce until they know. I'm 3cm and 60% and baby is -1 any thoughts and ideas would be good!!!