Bump measuring small -growth scan

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Has anyone else had this? My midwife measured me today and bump has only grown 1cm since last measurement around 3 weeks ago. So I’ve dropped from

The 50th percentile line to the 10th or just above. So being sent for grown scan in next couple of days. Is this quite common? I’m uk based and the bump measurements they do are just a rough guide and not deemed very accurate