Ultrasound baby weight accuracy

Is ultrasound baby weight accurate? I m 37w and Dr told me my baby is at 3.2kg, i wonder if baby weight via ultrasound is accurate coz i dont gain much weight though... And Dr also said, for normal delivery, baby should not be > 3.5kg, so i might be induced before EDD :s, else baby will be too big for normal delivery Appreciate your experience sharing!