Patient: At my first ultrasoundon 5/15 my baby was 4.2 centimeters long, which is the usual length for a fetus 9 weeks. I switched OB’s and my current OB says my due date is 12/27 meaning at my first ultrasound I was only 6 weeks. I read online that the first ultrasound is most accurate in determining age. Can somebody please tell me when my actual due date is!?
Doctor: Hello.thanks for contacting askthedoctor.comThe period of gestation is calculated from the last menstrual period . add 9 months and 7 days to lmp and you get the EDD.Ultrasonological dates are for the physician to understand and plan treatment and the edd are never accurate. So universally lmp is chosen as the marker to calculate pregnancy gestation.I hope your query is answered.regards