The gestational age of the pregnancy is measured from the first day of the last menstrual period. In this way of dating the pregnancy, the pregnancy is 40 weeks. As soon as data from the last menstrual period, the first accurate ultrasound examination, or both are obtained, the gestational age and the estimated due date.
How accurate are the menstrual and ultrasound pregnancy dating techniques? What are some of the issues and limitations for each method? The due date may be estimated by adding days (9 months and 7 days) to the first day of the last menstrual period (LMP). This is the method used by.