Ultrasounds performed after 22 weeks gestation cannot be used to estimate the due date of the baby because the size no longer reflects the age very well. Your ultrasound scan will be carried out by one of our highly qualified professionals in a caring and comfortable environment. These scans are only used to estimate the due date of your baby if this is all you have to go on. For the purposes of research and surveillance, the best obstetric estimate, rather than estimates based on the LMP alone, should be used as the measure for gestational age. Ultrasound Obstet Gynecol ;4: A nuchal translucency scan is part of the ultrasound scan that may give an indication of chromosomal abnormality. In some situations, such as when the scan is completed before 10 weeks of gestation or you are overweight, you may also need a vaginal scan.
What preparation do I need to do for a dating scan?
Your pregnancy and baby guide
But it is important to remember that only a few women go into labour on their due date, so it can be more helpful to think about the month in which you are expecting your baby, rather than the exact day. Accurate determination of gestational age can positively affect pregnancy outcomes. Early Pregnancy Scans are normally performed trans-abdominally through your tummy however an internal vaginal scan may be required at earlier gestations ie weeks to see all the necessary detail, or if your womb tilts backwards retroverted. Because of the risk of redating a small fetus that may be growth restricted, management decisions based on third-trimester ultrasonography alone are especially problematic; therefore, decisions need to be guided by careful consideration of the entire clinical picture and may require close surveillance, including repeat ultrasonography, to ensure appropriate interval growth. Accuracy of gestational age estimation by means of fetal crown—rump length measurement. Measurements of the CRL are more accurate the earlier in the first trimester that ultrasonography is performed 11, 15— No part of this publication may be reproduced, stored in a retrieval system, posted on the Internet, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission from the publisher.