I would defiantly wait too, I have a friend who was told it was a girl, ( which she desprately wanted after 3 boys) only to find out when she delivered the baby that is was another boy!. Mayb wait and see when you have another scan ( im not sure when that would be or mayb you could ask for another one). If you do get one and they still think it is a girl to ask for more evedince kwim?
hope the pregnancy goes well