Accuracy of ultrasound dating
This is because the fetus is growing so quickly that there is a big difference in size from week to week.
However, you will need to ask at the start of your scan, and your hospital may charge for this service.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.Even average babies can differ by up to 2 to 3 "weeks of growth";.These scans are only used to estimate the due date of your baby if this is all you have to go on.If you have more than one ultrasound during your pregnancy, giving you 'multiple dates', then the earliest ultrasound estimate should be used, because it will be more accurate.the baby and its heart beat can be detected relatively easily with trans-abdominal and trans-vaginal examination.
This is presuming that the pregnancy is actually at this stage of development.
If you have any questions about this, please feel free to talk to your sonographer or doctor about it.
An ultrasound scan sends sound waves through your womb (uterus). The echoes are then turned into an image on a screen that shows your baby’s position and movements.
For transvaginal ultrasound you can have an empty bladder Dating scans are usually recommended if there is doubt about the validity of the last menstrual period.
For example if you a tiny sac can be seen in the uterus, but the baby and its heart beat may not be detected yet.
Ultrasounds performed during the first 12 weeks of pregnancy are generally within 3 - 5 days of accuracy.