It is possible for a second ultrasound to lead to a change in the estimated due date, but it is not common for it to be off by as much as 2 weeks. Ultrasounds are generally accurate in determining gestational age during early pregnancy. However, there are factors that can affect the accuracy of the due date estimation, such as variations in fetal growth rates and individual differences. In some cases, if there is a significant difference between the first and second ultrasounds, healthcare providers may adjust the due date accordingly. It's important to remember that due dates are estimates and can vary slightly from person to person. If you have any concerns or questions about your due date, it's best to consult with your healthcare provider who can provide personalized guidance based on your specific situation.