Gender determination scans can be accurate at 18 weeks, but there is still a margin for error. It is not uncommon for different professionals to provide conflicting results. To make an informed decision, consider factors such as the experience and expertise of the specialists involved, the quality of the equipment used, and any additional information provided during the scan. If you are uncertain or want further confirmation, you can opt for another scan or consult with a specialist who specializes in fetal ultrasounds or prenatal diagnostics. Remember that gender determination scans are not foolproof and may have limitations due to various factors such as fetal position and visibility.