Ultrasound due dates can be accurate, but there is a margin of error. In some cases, the ultrasound due date may be off by a few days. This can happen due to various factors such as the baby's growth rate, positioning during the ultrasound, and individual differences in menstrual cycles. It is important to remember that an ultrasound due date is an estimate and not an exact science. If you believe your ultrasound due date is significantly inaccurate, it is best to consult with your healthcare provider for further evaluation and guidance. They may consider additional tests or adjustments based on your specific circumstances.