JJparents: When you go for the detailed scan, it will provide a better EDD estimate. In any case, the EDD is just an expected date. Although I don't have the stats, I'm pretty sure most women deliver outside of this EDD - some before, some after. If you're attending a pre-natal course, they will teach you (er.. more like your wife) to look out for symptoms such as labour pain, water bag dripping etc before making your way to the hospital.