This is Dr Shishir
Whenever there is reduced fluid in the sac the baby weight and baby's growth parameters are affected. As regards your query about the EDD, well the USG machine calculates the EDD based on the various parameters which are calculated at the time of the scan for eg. FL,BPD
,AC,HC etc. If at all there is a lag in these parameters then it will reflect in the EDD where in the machine will show a different date.
This however is not a cause of concern as in the late third trimester scans it is the Fetal weight which is of relevance and not the EDD.
The slight cause of concern in your case is the fact that amniotic fluid
is reduced. Please tell me what is the Fluid Index( something called AFI in the USG report) According to this index we can grade the severity of the reduction in fluid.
Be in consultation with your obstetrician as we need to be alert for any sign/symptom which is indicating fetal distress
further tests which your Obst may advice would be a repeat USg at 38-39 weeks, an obstetric Doppler, NST
Hope this helps