Doctors may want to induce

My baby girl has had a small waist for awhile now and she went from being in the 3% at 25 weeks to an 8% at 31 weeks back to a 3% at 34 weeks and they are worried that my placenta isn't working right but the rest of her body is right on track. They are saying she is 4 lbs 9 oz and are happy with my 25 pound weight gain. She passed her first nst yesterday and we will be getting another on Friday. Has anyone else had this problem and the doctors let you go till your due date?