How accurate are dating scans at 12 weeks
Most dating scans are done with a trans-abdominal transducer and a fullish bladder.
If the pregnancy is very early the gestation sac and fetus will not be big enough to see, so the transvaginal approach will give better pictures.
The nuchal scan provides a screening for chromosomal abnormalities such as Down Syndrome and is combined with a blood test.
The Harmony prenatal test is simply a non-invasive blood test that provides advanced screening for Down Syndrome.Non-invasive prenatal testing analyses microscopic traces of DNA from the unborn baby that circulate in a pregnant mother’s blood.The test screens for the three most common birth defects caused by chromosomal abnormality: A scan is performed to accurately date your pregnancy.If you have already had either the nuchal scan or integrated test and have received a high risk result you may consider this test to obtain a more accurate second opinion.
However the Harmony prenatal test is not 100% accurate nor diagnostic so we always recommend that you consider a diagnostic DNA test like a CVS or amniocentesis rather than having another screening test.
It can be performed from as early as 10 weeks and exceeds the screening accuracy of the 12 week nuchal scan but does not replace the actual ultrasound scan component of that service which should still be performed at around 12 weeks gestation.