I had a similar experience. At 33 weeks bub was 33, then at 36 the measurement went back to 31cm. Of course they scared me to death and I went for an u/s. Everything looked ok but they said the baby had a small head, big tummy and short legs. I could only picture a turtle. Well 3 weeks later she was born totally normal. So like some others have said, i am pretty sceptical about it all now. I think it's unfair to scare us so much. Especially when they are such small measurements. It all seems so much more, when in reality babies do vary in height. xo