Growth scan oddness

I've had growth scans at 28w, 31w, and this morning at 35w. The 28w showed our LO in the 31st percentile; the 31w said she'd dropped down to 18th percentile and weighing 3lb 9oz. This morning's 35w scan they told me she was 6lbs + (can't remember the oz they said) and in the 75th percentile! Either she has exploded in weight gain or those measurements are hella off. I was diagnosed with borderline GD but have been doing daily blood tests and my fasting and post-meal numbers are below range always. I also have had a plateau of weight gain. I am starting to hate ultrasounds because they seem so unreliable. I'm really hoping to avoid being induced, but we'll see what my OB says after she gets this morning's results.