It is not uncommon for there to be a slight difference between the gestational age determined by ultrasound and the estimated due date calculated based on the last menstrual period (LMP). This can occur due to variations in individual menstrual cycles and ovulation patterns. Ultrasounds are considered more accurate in determining gestational age because they measure specific fetal development milestones, such as crown-rump length or biparietal diameter. However, it's important to note that ultrasounds have a margin of error, typically within one to two weeks. In your case, a one-week difference may simply be attributed to these factors. It's also worth considering that if you have irregular periods or conceived shortly after your last period, this could further contribute to the discrepancy. To get a clearer understanding of your actual gestational age and due date, it is recommended to consult with your healthcare provider who can take into account both the ultrasound findings and LMP data. They will provide you with personalized guidance and ensure appropriate prenatal care throughout your pregnancy journey.