I had one when I was about 34/35 weeks the dr said I was measuring big which shocked me because he said I was measuring about 2 weeks bigger but i had only been measured the previous week an i was exactly spot on for my dates, an he said babys about 6.12 lbs yet he did all this by just putting his hands on my belly

never got tape measure out once, An I was scared becuase baby would be about 9/10 lbs when at term,
turned out i didnt have diabetes Just A lil extra fluid an I was slightly smaller for my dates an baby was infact 4lbs.5 an she was born at 39+6 wks at 7lbs10oz ,
so if you did need one in future good to no not to be worried becuase its not always true ;\)