How accurate is ultrasound dating at 16 weeks

Methods for Estimating the Due Date - ACOG

Using those results, along with other factors such as your age, your provider will be able to asses the risk of your baby having a neural tube defect NTD , Down syndrome, or other chromosomal defects. These screening blood tests are offered to every pregnant woman.

Important Information About Your Pregnancy

In contrast to the more invasive, diagnostic tests like amniocentesis or CVS, blood tests carry no risk to the pregnancy and they help identify pregnancies with increased risks. However, unlike those diagnostic tests, blood tests are non-invasive and carry no risk, whereas other more invasive, diagnostic tests, like an amniocentesis or a Chorionic Villus Sampling CVS in some rare cases lead to miscarriage.

There's no reason to have every patient undergo an invasive test if it's not necessary—so providers recommend additional testing only to those patients whose quadruple screen results indicate that their might be a genetic issue.

Methods for Estimating the Due Date

In other words, these tests do not offer "positive" or "negative," "yes" or "no" results, but increased risk predictions. In fact, the tests sometimes give a false-positive result. Along with the results from the quadruple screening, an ultrasound can aid your health care provider in determining whether additional testing is necessary. A sonographer can measure certain body parts on your baby-to-be to look for potential concerns. For example, increased thickness in the neck, a shorter-than-average nose length, and other physical clues might back up the high-risk results from the quadruple screen.

A prenatal blood screening that tests for the levels of certain substances in the bloodstream that might indicate genetic abnormalities in the fetus. In particular, the test looks at levels of alpha-fetoprotein AFP , a protein produced by the fetus 's liver and two hormones: Also called triple marker or second trimester screening test.

Can your pregnancy scan give the wrong due date?

In addition to detecting levels of AFP, hCG, and estriol, as with the triple screen, the quadruple screen also tests for another hormone, inhibin-A. The quadruple screen is sometimes referred to as the quad test or the second trimester screening test. Parents may receive compensation when you click through and purchase from links contained on this website.

First Ultrasound - Dating Ultrasound - 10 Weeks Pregnant

What It Would Look Like. You might just feel your baby move when you're 16 weeks pregnant! I have scans every few weeks so it will probably keep on changing. My baby will come when it's ready anyway, maybe weeks before or maybe weeks after my due date. These can be carried out from week 5 or 6 of pregnancy, which is a notoriously tricky time to be accurate on dates.

Measurements at such an early stage aren't accurate which is why they wait for 12 weeks to date you. Expert Jan Steward, who is director of Ultrasound Direct and Babybond, agrees that early scans carry a much greater risk of inaccuracy. We always recommend mums get a definitive dating scan closer to 12 weeks as this will be much more accurate. Just half a millimetre at such an early stage can change your date by a week. Your week scan will be far more accurate. The sonographer then said that I was only about 4.

Then at the week scan I got an EDD of 15 march, so that early scan was completely out. Well, you'd think so, wouldn't you. At around 12 weeks you can get more accurate measurements. By talking to the health care professionals you should get a clearer picture as to what is happening. Thanks so much for your post — we always welcome feedback, positive or negative, as we always aim to make our articles as accurate and as helpful as possible. We spent a lot of time talking to sonographers before writing this article, so we're surprised that you think what they're saying is not in line with what you have studied.

We'd be really keen to know more about your studies — and what you have learned.

Women's Health Care Physicians

You're right that we did include 'anecdotal stories' in our article. We used them to illustrate the key points we were making in the articles but the quotes we used were all centred on the real experiences of pregnant women posting in our forum.


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We are confident that we are not using these quotes to 'misinform women', as the key points in our article were all sourced from expert monographers. It's interesting that you say that ultrasounds between 8 and 10 weeks are the most accurate. In the UK, most pregnant women don't have an ultrasound until they are at least 12 weeks pregnant.


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  6. Perhaps you are based in the US, or another country, where ultrasound practice is a bit different? We use cookies to improve your experience of our website. Skip to main content. Find us on YouTube Twitter Pinterest. Can your pregnancy scan give the wrong due date? Some of the information in this article disagrees with everything we have studied so far regarding dating pregnancies and ultrasound accuracy.