My amniotic fluid is reduced at 30weeks+4days?

Hi,im due 14/08/2011 and my midwife referred me for a growth scan as is my first baby,im only 18years of age and im of small structure...when they carried out the scan they discovered that the amniotic fluid has reduced yet there was no evidence of SRM and also that her abdominal circumference isnt what it should be for how far she is,everything else was fine on the scan,The doctors have now really scared me,they didnt explain any good things from the scan,just that they want to keep a check on her and have booked me for another scan in 2weeks.Should i be worried?