Am J Obstet Gynecol. If your LMP-estimated due date is very different from your dating scan-estimated due date, your doctor may express concern. Prevention of Rh D alloimmunization. Please try again.
In those instances, doctors may take a wait-and-see approach to see if a woman is going to deliver soon, but may opt to induce if they feel labor is not imminent, he said. However, in the first trimester there is very little variation in fetal size, and so it turns out that an ultrasound done between 7 and 13 weeks is the most accurate. Management of Postterm Pregnancy.