EDD means EXPECTED/ ESTIMATED Date of Delivery, and is usually give or take 2 weeks. You can't really be sure kung kailan ka manganganak kahit pa 100% sure ka sa LMP mo or date of conception, or anuman nakalagay sa ultrasound. Kasi hindi naman guarantee na saktong after 40 weeks ka manganganak.
Personally mas sinusunod ko yung based sa LMP since the ultrasound is usually based on baby's actual size/ development kaya pabago-bago.
janell arpon