Evidence suggests that ultrasounds more accurately predict your due date than using your last menstrual period—but only in the first trimester and early second trimester (until roughly 20 weeks). 3 Early ultrasound due dates have a margin of error of roughly 1.2 weeks.

Which pregnancy scan is accurate?

The most accurate way to date a pregnancy is with an ultrasound done between 6 weeks and 8 weeks, 6 days, according to Dr. Michael Cackovic, MD, an OB-GYN with The Ohio State University Wexner Medical Center.

Which is more accurate CT or ultrasound?

Conclusion. CT misses fewer cases than ultrasound, but both ultrasound and CT can reliably detect common diagnoses causing acute abdominal pain. Ultrasound sensitivity was largely not influenced by patient characteristics and reader experience.