But if thin patient, experienced operator of the ultrasound and good views it can be very accurate. Otherwise, you might want to check the dates you provided. Read more First trimester ultrasound is accurate within 5-7 days.. Au/services/pregnancy-ultrasound-5-17-weeks-dating-and-viability. The fact that these 2 ultrasounds agree means that you have very accurate dating. Also if you are uncertain about your LMP, most OB's will use that early US. Read more 14 week ultrasound is on the cusp between first and 2nd trimester. (if the number did not already have the 2 weeks added on, then the number would be the "age of the fetus", which is 2 weeks less than the "number of weeks pregnant") ...There is no test that can date conception more accurately than a 1 week window. First trimester ultrasound usually accurate to 3-5 days. So at 14 weeks I would doubt the dates would be 2w3d off. In fact, it's thought that only around four percent of women give birth naturally on their due date.If you still have questions, learn more about the accuracy of ultrasound in predicting your due date.Here's some info about the reliability of ultrasound for different pregnancy concerns.When you've finished looking at these topics, you may enjoy looking at our collection of ultrasound photos week by week through pregnancy.In your later second (after 20 weeks), and especially in your third trimester, your estimated due date shouldn't change based on an ultrasound because it will be less accurate.
These pictures show up on a computer screen at your bedside during the test.If your pregnancy has a gestational age of less than eight weeks (between six and eight weeks), a transvaginal ultrasound (inserting the ultrasound probe into your vagina) is usually needed for accurate results.It's important to note that hand-held ultrasound or fetal Doppler may not detect the baby's heartbeat until you are 12 weeks along in your pregnancy.But ultrasounds are not 100 percent reliable for everything they measure.