My due date as of my last period was 9th September.. my dating ultrasound at 5 weeks 4 days was 8th September and my scan at 18 weeks showed to be around the 4th September. But with all those dates the hospital is going by the first date of the 9th September. Those scans are only going by the size of the baby and how fast its growing. I dont think a few days either way is something to be concerned about as rarely are babies born on their due date. Dont stress too much..