Hay, same worry ko yan dati! The thing is, ang dating ng ultrasound ay medyo subjective lagi especially kung late ka mag-ultrasound sa pregnancy, kaya 1 week difference is totally normal at hindi reason to rush into CS kung healthy ang baby mo. I'd really suggest you check with your OB about the dating discrepancy at what signs to watch for, some of my mum friends who were worried went for regular NST (non-stress tests) instead of jumping to CS, at it gave them peace of mind na everything was fine, so maybe that's something to ask your doctor about din?