nadia_f on "Identical Twins Measuring 5 days behind"

Hi everyone,
I am really concerned. I am currently 9w4d pregnant and had an u/s today and my identical twins both measuring 5 days behind. Last week at the u/s they were measuring 4 days behind. Do I need to worry? Has anyone had IT measuring this much behind and still went on having a normal pregnancy? Please help. Thanks in advance. Lucky